Endorsed courses on Chess.com
A verified endorsement of a course means that a titled player has reviewed and approved the variations it contains. Since titled players are often extremely busy pursuing their careers, Chess.com offers their students the opportunity to bring their courses to the platform while giving the titled players due credit for verifying the playability of the lines.
Most, if not all lines in an endorsed course have been hand-picked by the titled player. However, usually support, and commentary are provided by the course owner who may not be as highly ranked but can provide some guidance. It is then up to the community to bring the course up to the level they desire by collaborating together on the variations included.
By working on such a model, master-quality courses can be available at a lower price than if the course was fully maintained by the masters themselves.
How do I know when a course is being endorsed?
You can identify a course endorsed by a titled player because their name will be displayed next to the course author's name.
In the screenshot below, the 'Chess Candidates 2022' course by Chessable is endorsed by GM Anish Giri.
There are currently only a few such courses. Most courses are written by the authors themselves and this does not apply to them.