Understanding blockwatcher

This part answers what blockwatcher is before any of it needs to run: the problem it exists to solve, the shape of the pipeline it builds for you, and the vocabulary the rest of the wiki assumes you already have. Read it first if you are deciding whether blockwatcher fits your problem, or if a later page uses a term you have not seen defined yet.

• What is blockwatcher?: the problem blockwatcher solves and how it differs from a bespoke listener script.
• How it works in one picture: the pipeline every network runs, traced step by step.
• Glossary: every term the wiki uses, defined against the actual code.