TedEd is a collection of original animated videos lessons. You can choose by subject and view the video in class or assign it as homework. Every video is accompanied by a lesson with multiple choice questions that check your general comprehension. If your answers are wrong, you can always check with the video hint. There is also a Think section with questions that further explore the topic.
For teachers, one of the most powerful features is the Customize your Lesson area, where you can customize the lesson by editing the title, giving your own instructions, selecting or deselecting multiple choice questions…etc.