PPP stands for presentation, practice and production. It's a way of structuring a language lesson when you are presenting grammar, functions or vocabulary for the first time.
Presentation is where an explanation of the language takes place. This is usually led by the teacher. In this phase, it's important to show (1) how and when to use the language point, (2) how to structure it eg to be, subject and verb -ing for present continuous questions, and (3) how to pronounce it. You need lots of explanation, demonstration and focus on the structure in this phase.
In the second phase, the students need controlled practice of the language. This can be spoken or written, but do make sure that the students get spoken practice at some point. To practise making present continuous questions, they could make questions from prompts. Alternatively in pairs, one student could mime and the other says "are you singing? are you watching TV?" etc.
In the last phase (production), free practice takes place. An activity needs to be devised where the language presented would occur naturally. This should relate to the students' personal lives where possible. For present continuous questions, this could be asking questions such as "what is xxxx doing at the moment?" about members of family, friends etc.
PPP is a good framework for teaching language at low levels. However, the teacher shouldn't assume that students know the language after one PPP lesson.