AggregatorV3Interface is the contract name of the Chainlink oracle to obtain prices.
How are we using it?
We use it to get the Index Price (see: Key Terms) of the trading pairs we trade in the market (e.g. ETHUSD). This price is needed to compute the funding rate to avoid having the price in the protocol move too much from the price of the real asset (see the Funding section to learn more about funding rates).
We also use it to obtain the USD worth of allowlisted non-USD collateral assets. For example, if WETH is an allowlist collateral, we can use this to get the oracle price of WETHUSD and obtain the USD worth of WETH. Learn more about collateral types in UA and how it affects the system in Margin and Liquidations.