A Bitcoin Improvement Proposal (BIP) is a formal document that outlines a proposed change or improvement to the Bitcoin protocol. The Bitcoin protocol is the underlying set of rules and processes that govern the Bitcoin network, including how transactions are verified, how new blocks are added to the blockchain and how the network operates as a whole.

BIPs are designed to be a collaborative and transparent process for proposing, discussing and implementing changes to the Bitcoin protocol. Any member of the Bitcoin community can submit a BIP, which typically includes a detailed technical specification of the proposed change, as well as a justification for why the change is necessary or desirable.