A skill is a reusable set of instructions that turns your AI into a specialist for one job, like writing your offer or your sales page.
Without a skill, you ask the AI for a sales page and it guesses. It guesses the same way for everyone, which is why so much AI copy sounds alike.
With a skill, the AI asks you the questions a good copywriter would, in the right order, one at a time. Then it writes from your answers, your audience's words and your examples.
You use the skills in your own Claude or ChatGPT account. There's no coding and nothing to install on your computer. See How to add the skills to Claude or How to use the skills in ChatGPT.