Quizlet helps students to study sets of key terms or diagrams - think digital flashcards with increased interactivity. It also links with Google Classroom, so you can share sets that you create with students seamlessly. The app is free, but if you would like to track student progress then you can upgrade for an annual fee. Many students are already familiar with Quizlet, especially examination groups. I have created sets of for A Level and IB courses, which I then share directly with students through a class code. You can, however, ask students to create their own or look for others that have already produced sets and amend accordingly. I highly recommend the Quizlet Live feature for an in class activity - the boys love it.