abc… Letters
123… Digits
\d any Digit
. any Character
\. Period
[abc] Only a, b, or c
[^abc] Not a, b, nor c
[a-z] Characters a to z
[0-9] Numbers 0 to 9
{m} m Repetitions
{m,n} m to n Repetitions
* Zero or more repetitions
+ One or more repetitions
? Optional
\s any Whitespace
^…$ Starts and ends
() capture Group
(a(bc)) capture Sub group
(.*) capture Variable content
(a|b) Matchs a or b
\w any Alphanumeric character
\W any Non-alphanumeric character
\d any Digit
\D any Non-digit character
\s any Whitespace
\S any Non-whitespace character