Avalanche is a Proof of Stake (PoS), layer 1 platform that features 3 built-in blockchains: Exchange Chain (X-Chain), Platform Chain (P-Chain), and Contract Chain (C-Chain).
Infura provides access to the C-Chain only.
The C-Chain supports the Ethereum Virtual Machine (EVM), allowing Ethereum developers to deploy Solidity smart contract dapps onto the C-Chain. Dapps can run on both Avalanche and Ethereum. Avalanche Platform's C-Chain is EVM-compatible, but it is not identical. There are some differences you need to be aware of, otherwise, you may create subtle bugs or inconsistencies in how your dapps behave.