Website: https://cosmos.network/ibc & https://www.ibcprotocol.dev/

docs: https://tutorials.cosmos.network/academy/1-what-is-cosmos/

High-level overview of IBC

• IBC/TAO(The transport layer) comprises the Transport, Authentication, and Ordering of packets, i.e. the infrastructure layer.
• IBC/APP consists of the application handlers for the data packets being passed over the transport layer. These include but are not limited to fungible token transfers (ICS-20), NFT transfers (ICS-721), and interchain accounts (ICS-27).
• Application module: groups any application, middleware or smart contract that may wrap downsteam application handlers to provide enhanced functionality.