Several weeks ago I deliberately provoked a discussion/argument about the difference between analog data and digital data.
Naturally, the Nyquist sampling theorem got drawn into the discussion. I couldn't find my "preferred" textbook with a visual description of sampling, but it just came to hand.
It's Lathi's "An Introduction to Random Signals and Communications Theory". (40 years ago, it cost $14, a huge amount of money.)
On page 47 you'll find an excellent graphical "explanation" of the sampling theorem.
No response is needed; I'm not trying to reopen the discussion, just provide some good documentation.