A pull request packages the diff, discussion, checks, and reviewer approvals around a change. In agentic workflows, it is often the boundary between generated work and human release decision.
ELI5
Think of Pull Request as a tool from the builder toolbox. A request to review and merge code changes from one branch into another.
In practice
Use it when you are installing, editing, testing, reviewing, or shipping code. In practice, define the owner, input, output, and failure mode before you rely on it.