It is basically a guess-the-move game. You play along as the GM you picked from the list in a game he won, and try to guess what move he played. If you guess a differet move, you are scored based on the computer evaluation of the move you picked. Guess-the-move is a pretty standard training mode that does a lot of good. This is not the optimal way to play guess-the-move, but it is a pretty decent approximation. The optimal way to play guess-the-move would be to compare your analysis with master-level annotations of the correct move each time to learn where you lined up with the thought process and where you were going astray and/or missed important things.
Lucas Chess's "Play like a grandmaster"

A good feature. But there are only 3 GMs to choose from , Carlsen , Fischer and Capablanca. I wish there were more.

A good feature. But there are only 3 GMs to choose from , Carlsen , Fischer and Capablanca. I wish there were more.
I've never used this feature, but it appears that you can import other GM's games from the web.

That's correct. Just start the import function and it will populate it with what looks like hundreds of players. You can also import manually with any PGN you'd like.

Yes, you can import many games from GMs. I have downloaded Tal's games to try to see what he saw, but it's not easy!
There used to be a guy on here that knew a lot about Lucas chess, but I think he is banned now.

Don't forget Fred Mellender's free "Guess The Move" program:
https://sites.google.com/site/fredm/
Someday I might compare the two to see which I like better.
Hi,
What exactly does Lucas Chess's "Play like a Grandmaster" option do? I mean, in what way does it help us? I've seen that it opens up a dialog box saying that a certain champion played so-and-so move in such-and-such position, but is that it?
Best Regards,
Aashish