Are there some documents about each lessons that summarize the contents?

Hi Pietro, there are workspaces for you to demo code and concepts in, forums and lesson notes.

Hope this helps

Yep. But could be a good idea to have simple pdf with important conceps of every single lessons.

Hi Pietro, if you print in chrome you can make your own PDF notes, not saying your idea has no merit, but I think it would only benefit a tiny segment of all users and would slow the rate of course production as there would then be an authoring, editorial etc process for each PDF

yes. But for examples... in the array of javascript http://teamtreehouse.com/library/javascript-foundations/arrays/methods-part-3 have a little "text guide" about the the type of array methods. I know that this could need more work but it could help at the beginnings.! However thx for the comments!

what about using resources like w3schools who cover a reference guide for this, I'm not sure if treehouse is meant to replace books, websites and reading etc (at least I hope not)

Skillcrush provides cheatsheets for their blueprint courses so I don't see why Treehouse couldn't do the same thing.