These games work well in class with an interactive whiteboard, although students can also use them for self study on mobile devices or on computers (especially if you have a large class). In small classes, they work best with teams of about three students at the board taking it in turns, and a time limit. The rest of the class can watch (and shout out clues or distractors if you like a noisy classroom) before they take their turn. Most of the games are ready-made, but with some (e.g. Puzzgrid) you or your students can design your own quizzes.