I don't know a lot about regex. I don't assume that many people know about how regex is. Regex can be very useful.
https://regex101.com is your friend.
A lot of Regex tutorials or even makeshift Regex guides kind of miss the mark.
Here are some basics
Matching Characters:
. (dot): Matches any single character except newline.
[a-z]: Matches any lowercase letter.
[A-Z]: Matches any uppercase letter.
[0-9]: Matches any digit.
\w (word character): Matches any alphanumeric character (a-z, A-Z, 0-9, and underscore).
\s (whitespace): Matches any whitespace character (space, tab, newline).
Quantifiers:
*: Matches zero or more of the preceding element.
+: Matches one or more of the preceding element.
?: Matches zero or one of the preceding element.
{n}: Matches exactly n occurrences of the preceding element.
{m,n}: Matches between m and n occurrences of the preceding element.
Anchors:
^: Matches the beginning of the string.
$: Matches the end of the string.
Grouping:
(): Groups characters for repeated matching or capturing.
Other Symbols:
\d: Matches any digit (equivalent to [0-9]).
\D: Matches any non-digit (opposite of \d).
\b: Matches a word boundary (beginning or end of a word).
\: Escapes the special meaning of a following character.