What is a Bitcoin Improvement Proposal (BIP)?

A BIP (Bitcoin Improvement Proposal) is the document standard used for proposing changes to Bitcoin. 

Proposals are usually first roughly outlined using a mailing list of developers, where feedback and their feasibility are assessed before a decision is made to create a full BIP document, which is then shared on GitHub. At this point the proposal is peer-reviewed by developers who agree on which ones to go forward with and implement when consensus is found.

There are three types of BIPs:

1. A Standards Track BIP, used for changes that would alter the way Bitcoin works, such as how blocks or transactions are processed (such as SegWit) or for how Bitcoin integrates with third parties.
2. An Informational BIP, as the name suggests, is used for providing information to developers about potential issues and solutions to Bitcoin. These BIPs are not voted on and can be ignored by the community.
3. A Process BIP, similar to Standards Track BIPs, these proposals are used for outlining changes to how Bitcoin developments and processes are carried out, such as BIPs themselves or how they are voted upon.