In short: They’ve made a bunch of cool YouTube videos. The videos aren’t too strong as stand alone material, but the simple, clear (but natural) language make them great supplemental material for teachers.
For students: If you join, you can use the comprehension questions that come with a lot of videos and readings.
For teachers: Do the free trial at holmwoods.eu to check out some more material. Things are set up for your students to do homework here. Higher level students would get the most out of it.