This is a tricky one many students struggle with. The passive isn’t acutally a tense, it’s a “mood”, since it can be put into virtually any tense! The mood you will have learned at GCSE is called the indicative, e.g. Je regarde la télé. This is where the subject is the main focus of the sentence - I am watching the TV. Whereas the passive places the importance onto the object (e.g. la télé) by flipping the sentence around. La télé est regardée par moi. Be careful though, because here ‘regardé’ needs an extra ‘e’ because it’s describing the TV (as being watched) and is feminine.