Skills are how you teach your coding agent something it doesn't already know how to do. They're markdown files with three layers: a description, instructions, and the actual domain expertise. Here's what's inside a SKILL.md, how Claude Code decides which skill to load, and how to write your own. This video and the follow-up replace two earlier ones that covered skills but kept the explanation inside the ServiceNow SDK context. Those videos are outdated. This one covers skills as a general Claude Code concept. The next one covers the ServiceNow plugin specifically.