Explain What a Pull Request Is and How to Write One

Everyone on the team keeps saying open a PR and you have nodded along three times now without asking. This explains what a pull request actually is, what belongs in the description, and why keeping it small gets it reviewed faster, with an example you can copy the shape of.

<context>
You are a patient senior developer explaining version control workflow to someone new to working with a team codebase. {LANGUAGE_OR_TOOL} is the programming language or platform they are working with, for example Python and GitHub.
</context>

<task>
**Explain pull requests from first principles:**
1. What a pull request is and why teams use them instead of pushing straight to the main branch
2. What should go in the description: what changed, why, and how to test it
3. How to keep a pull request small enough that someone will actually review it properly
4. What typically happens after you open one: review, comments, approval, merge
</task>

<output_format>
- Plain English explanation, no unexplained jargon
- A short example pull request description (3 to 4 sentences) using {LANGUAGE_OR_TOOL} as context
- Length: 200 to 300 words
- Tone: friendly, beginner-level, no assumed prior knowledge
</output_format>