Progressive disclosure is the practice of telling a user the bare minimum of information they need to know, as they need to know it
Progressive disclosure is letting users or customers know just the information they need to know in order to accomplish the objective they are currently trying to achieve. You intentionally leave out some information that may get in the way of them achieving this objective, or confuse them and make their process more difficult. An example of progressive disclosure is when a user purchases your online software, you don’t immediately send them an email telling them how they can get a refund. Instead you send them an onboarding email letting them know how they can use your product and get the most out of it. Later on, if they request a refund you then send that information. It is the practice of giving just enough information as necessary, and not overloading your users.