AIDA is an acronym used in marketing and advertising to describe the stages that a customer goes through in the purchase process.
The stages of Attention, Interest, Desire and Action, generically follow a series of cognitive (thinking) and affective (feeling) stages culminating in a behaviour (doing e.g. purchase).
When it comes to persuasive design, users go through a few stages between Awareness and Action, and the design should guide them from one stage to the next and include:
Original author / source: Smashing Magazine