An AI skill is a reusable set of instructions that helps an AI tool handle a particular kind of task. It may include a checklist, examples, or small supporting files.
For example, a writing skill might tell an AI how to research a topic, explain it simply, and check its sources. The user can ask for that kind of work without repeating the whole process each time.
A skill explains how to work; it does not automatically provide new permissions or tools. The AI can only use the access its app already allows.