Auto-generate filenames in SHELL?

Question

bash

Good afternoon. SHELL is known to support auto-generation of filenames and commands like this
> cat *.txt
work fine. I really want to know more about this magic, in particular, I'm interested in the question of what special characters mean ^,! и {}in the context of auto-generation.
And the main question is how to display the contents of directories (ls) whose names consist of only three characters by means of this very generation?
Advise a book or man, where it is described)
PS for a student, I want to pass a lab (Google fails with this question fails)

Answer 1

This is a wildcard, something like a small simplified regexp :
www.linfo.org/wildcard.html
ryanstutorials.net/linuxtutorial/wildcards.php -vyra...