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.