# Architecture

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​The Parallel Protocol is a collection of decentralized and non-custodial smart contracts built to support the rest of the Decentralised Finance (DeFi) ecosystem:

* **Vaults Core:** The main contract to interact with the Parallel protocol. All calculations happen here.
* **Vaults Core State**: Owns the global state (cumulative rates & last refresh) for each collateral type available to borrow against. All state updates & calculations happen here
* **PAR**: PAR is a standard ERC20 tokens, whose value is pegged to the EUR fiat currency.
* **paUSD**: paUSD is a standard ERC20 tokens, whose value is pegged to the USD fiat currency
* **Rates Manager**: Stateless. Calculates debt and fees for each Vault.
* **Liquidation Manager**: Stateless. Calculates health factors and liquidation variables.
* **PriceFeed:** Responsible for retrieving collateral prices in fiat, for calculating Vault health factors.
* **FeeDistributor:** Responsible for collecting and distributing protocol fees.
* **AddressProvider:** Indexes all module addresses read by other modules.
* **ConfigProvider:** Responsible for updating protocol config parameters.
* **VaultsDataProvider:** Owns vault state, base debt, and vault related read functions.