Attention → Interest → Desire → Action. A 100-year-old copy formula that still works.
AIDA is the structure of almost every piece of sales copy ever written. Get Attention (headline/hook). Build Interest (why this matters to you specifically). Create Desire (paint the picture of having this). Call to Action (tell them exactly what to do next). Not every piece follows AIDA explicitly, but the structure is hiding in almost all of it.
AIDA is training wheels for copywriting. If you're writing a piece of sales copy and it's not working, check whether each section is doing its job. Missing an A, I, D, or A? That's usually where it breaks down.