What is "progressive disclosure"?
Progressive disclosure is an interaction design technique that sequences information and actions across several screens in order to reduce feelings of overwhelm for the user. By disclosing information progressively, you reveal only the essentials and help the user manage the complexity of feature-rich sites or applications. Progressive disclosure follows the typical notion of moving from "abstract to specific"; only it may mean sequencing interactions and not necessarily level of detail (information). In other words, progressive disclosure is not just about displaying abstract then specific information, but rather about 'ramping up' the user from simple to more complex actions.