You can opt to password protect your quizzes if you wish or keep them public. It is easy to share the link and students can complete the wide variety of quizzes to help them learn. There is also an app to download should students wish to.
I used this last year to set my year 11 a quizlet challenge - between 19 and 20 of the crucial German words each week.(here for challenge) Feedback about the site was very positive and I now use it weekly with my AS group too.
It is very easy and quick to use and, although I always create my own sets to suit my students, there are tons of sets already created and shared by lots of kind teachers out there. Alternatively, get students to create and share their own sets. Enjoy!