# Key Concepts Learn how Polyester moves Assets across chains, keeps balances on-chain, and processes order-book trades. To use Polyester confidently, it helps to understand how Assets move, where balances live, and how trades are processed. These concepts follow an Asset from its source chain into Polyester, through your account, and onto an order book. ## Core Systems ### Polyester Chain Polyester Chain is Polyester's EVM-compatible Layer 1. It is the on-chain foundation of the Polyester Exchange and Zipper, where Zipped Assets, Safe smart accounts, Funding Account balances, and the Trading Gateway and Zipper contracts live. Validators verify every transaction and agree on each new block. This creates a shared, publicly auditable record of Asset supplies, balances, account controls, and protocol activity that you can view through Polyester Scan. [Polyester Chain How the chain, accounts, and on-chain balances work.](https://testnet.polyester.com/docs/user-docs/polyester-chain/overview) ### Zipper Zipper connects supported external chains to Polyester. It wraps ("zips") external Assets into tokens on Polyester Chain and unwraps ("unzips") them for supported Withdrawals. Every Zipped Asset stays tied to its exact Asset and source chain. Zipper validates Deposits and Withdrawals while keeping the supply, backing, and Withdrawal path for each route separate. #### Zipped Assets A **Zipped Asset** is an ERC-20 token on Polyester Chain that represents an Asset from an external chain. Its on-chain supply is backed 1:1 by the equivalent Asset held in that route's vault on the original source chain. ### Example: Separate zUSDT routes If 100 USDT is deposited throughEthereum and 50USDT throughSolana , Polyester creates 100EthereumzUSDT and 50SolanazUSDT. These are independent Zipped Assets with separate supplies and backing. The Asset held in the vault on the original source chain and the corresponding Zipped Asset supply on Polyester Chain are both publicly auditable. Each route remains independent, so its supply, backing, and Withdrawal path can be verified separately. [Zipper How source-chain Assets become Zipped Assets and Unified Assets.](https://testnet.polyester.com/docs/user-docs/zipper/overview) ### PolyEngine PolyEngine powers Polyester's order-book trading, settlement, and lending liquidations. It maintains order books, reserves balances, matches Orders, settles Fills, and provides API connectivity for market makers, high-frequency traders, AI agents, and other services. PolyEngine matches up to 1 million transactions per second, with 1 ms 99th percentile (P99) latency. This gives traders institutional-grade execution speed, while PolyEngine's reservation, settlement, and liquidation controls keep balances, trades, and lending positions consistent throughout their lifecycle. [PolyEngine Order matching, settlement, and API connectivity.](https://testnet.polyester.com/docs/user-docs/polyengine/overview) ### Polyester Scan Polyester Scan is Polyester's blockchain Explorer. Use it to view public records for blocks, Transactions, contracts, Zipped Assets, and Deposit and Withdrawal Flows. Polyester Scan focuses on public chain evidence. Private credentials, account balances, active Orders, Fill attribution, and the internal trading ledger remain outside the public Explorer. [Polyester Scan Public records for blocks, Transactions, and Flows.](https://testnet.polyester.com/docs/user-docs/polyester-scan/overview) ## Accounts and Balances ### Smart Wallet Your smart wallet is the on-chain account controlled by your connected or embedded owner wallet. It authorizes account activity on Polyester Chain while your owner wallet remains in control of your private keys. The smart wallet establishes who can act on the account. Zipper custody paths and Polyester application contracts separately hold or account for Assets as they move through supported products. Polyester sponsors the gas fees for current user-facing activity on Polyester Chain, so you can authorize on-chain actions without holding its native gas Asset. This gas abstraction applies to Polyester Chain. External chains still charge their own transaction fees. [Smart wallet The on-chain account your owner wallet controls.](https://testnet.polyester.com/docs/user-docs/polyester-chain/smart-account) [Gas abstraction How Polyester sponsors gas on Polyester Chain.](https://testnet.polyester.com/docs/user-docs/polyester-chain/gasless-transactions) ### Funding Account The Funding Account is where you manage on-chain balances for Deposits, Withdrawals, internal transfers, and transfers to Trading. When a supported Deposit arrives, Polyester keeps the Zipped Asset as backing and credits the matching Unified Asset balance to Funding. > Zipper credits deposits directly to your Polyester Funding or Trading Account under your smart wallet's control. You never need to receive or hold Zipped Assets in MetaMask, Phantom, or another external wallet. Assets remain outside the lending liquidation engine while they are in Funding, so they cannot be liquidated or used as collateral for margin trading. Transfer a balance to the Unified Trading Account when you want to use it for an Order. [Funding Account On-chain balances for deposits, withdrawals, and transfers.](https://testnet.polyester.com/docs/user-docs/funds/funding-account) ### Unified Assets A **Unified Asset** combines supported versions of the same Asset into one Funding or Trading balance. Polyester explicitly assigns eligible Zipped Asset routes to the same Unified Asset, so a matching ticker or wrapped variant alone does not combine them. A Unified Asset is an on-chain accounting record rather than an ERC-20 token. It is publicly auditable, while every Zipped Asset beneath it keeps its own token supply and 1:1 vault backing. [Unified Assets On-chain balances for deposits, withdrawals, and transfers.](https://testnet.polyester.com/docs/user-docs/funds/unified-assets) ### Example: Combine zUSDT into one balance A user's 100 EthereumzUSDT and 50SolanazUSDT appear as one 150uUSDT balance for Funding and Trading. Polyester still tracks eachzUSDT supply and its source-chain backing separately. ### Unified Trading Account The Unified Trading Account holds the private balances you use for trading. When you transfer a balance from Funding to Trading, PolyEngine can use it to create and settle Orders for that Asset. Each Trading balance shows a total, available, and reserved amount. Active Orders and other pending activity can reserve part of the balance until they Fill, are canceled, or reach another final state. [Unified Trading Account Private balances used to place and settle Orders.](https://testnet.polyester.com/docs/user-docs/funds/trading-account) ### Main Accounts and Subaccounts A **Main Account** is your top-level Polyester account. It controls account-wide settings, security, the VIP tier, and every Subaccount created beneath it. All Subaccounts share the Main Account's VIP tier. A Subaccount gives you a separate environment for balances, members, policies, activity, and API keys. Each Subaccount has its own Funding and Trading balances. Switching the active account changes which balances, Orders, and permissions you are managing. [Subaccounts Separate balances, members, and API keys under a Main Account.](https://testnet.polyester.com/docs/user-docs/subaccounts/subaccounts-overview) ## Trading ### Pair A **Pair** is one market between two Assets: a base Asset and a quote Asset. Every Pair has its own order book where those Assets can be bought and sold. The source chain does not change the Pair. Supported versions of each Asset trade through the same Unified Asset balance and order book. ### Example: ETH/USDT across multiple source chains The ![ETH](https://testnet.polyester.com/icons/tokens/eth.svg)![USDT](https://testnet.polyester.com/icons/tokens/usdt.svg) ETH/USDT Pair tradesuETH againstuUSDT.ETH deposited fromBase orArbitrum becomes part of the sameuETH Trading balance, whileUSDT deposited fromEthereum orSolana becomes part of the sameuUSDT balance. Polyester uses one![ETH](https://testnet.polyester.com/icons/tokens/eth.svg)![USDT](https://testnet.polyester.com/icons/tokens/usdt.svg) ETH/USDT order book, not a separate Pair for each source chain. ### Order Book An **order book** lists the buy and sell Orders available for one Pair. Polyester uses price-time priority: the best price comes first, and earlier Orders take priority when multiple Orders have the same price. PolyEngine maintains a separate order book for every Pair. Its liquidity comes from balances held in Polyester Unified Trading Accounts rather than an external DEX, AMM, bridge pool, exchange, or third-party solver. ## How These Concepts Fit Together Follow an Asset through Polyester from Deposit to Withdrawal: - Your smart wallet authorizes the account on Polyester Chain. - Zipper brings a supported Asset into Polyester from its source chain. - The Deposit creates a source-chain-specific Zipped Asset backed 1:1 by the original Asset. - The Funding Account combines eligible Zipped Assets into one Unified Asset balance. - Moving that balance to the Unified Trading Account makes it available to PolyEngine. - PolyEngine accepts and matches Orders on the Pair's order book. - Fills update private Trading records, while Market Trades publish completed exchange activity. - Move funds back to the Funding Account before making a supported external Withdrawal. - Polyester Scan shows the public chain and cross-chain Flow records for the journey.