Can anyone help me with Regex?

Question

I don't understand it...
I need someone that can help me.

Answer 1

A regular expression is a sequence of characters that specifies a search pattern. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation. It is a technique developed in theoretical computer science and formal language theory.
https://en.m.wikipedia.org/wiki/Regular_expression

Answer 2

For example:
.(dot) Matches any character.

^regex - Finds regex that must match at the beginning of the line.
regex$ - Finds regex that must match at the end of the line.

[abc] - Set definition, can match the letter a or b or c.

thanks and happy coding