Stephen Wolfram: Language, Mathematica, Alpha, Lab, Etc.

https://www.stephenwolfram.com

Language, Introduction:

https://www.wolfram.com/language/elementary-introduction/2nd-ed/

Cloud: https://www.open.wolframcloud.com/env/wpl/GetStarted.nb?funnel=WPLExplorations#sidebar=explorations

Physics: Visual Summary https://www.wolframphysics.org/visual-summary/dark/