The Basic plan gives full access to the "Watch" section. This lets you watch videos with the assistance of the interactive captions. You can click on any word to see its translation, grammar structure and to watch clips of it being used in other contexts. This plan is meant to help you learn new vocab and work on your listening-comprehension. There are also several fully-featured videos that allow access to their quiz section. However, all of the quizzes are only available on the Plus plan.
The Plus plan gives full access to all of our features. It gives you exercises on the vocab you've seen in the videos. Quiz mode lets you learn through personalization (the prompts are personalized for you based what you've learned on FluentU). You also have access to Ready for Review, a spaced repetition system, designed to have you review vocab right when you're likely to forget it, to maximize retention. You also get access to personalized flashcards and printable PDFs of each video's transcript.