. - Any Character Except New Line
\d - Digit (0-9)
\D - Not a Digit (0-9)
\w - Word Character (a-z, A-Z, 0-9, _)
\W - Not a Word Character
\s - Whitespace (space, tab, newline)
\S - Not Whitespace (space, tab, newline)
\b - Word Boundary
\B - Not a Word Boundary
^ - Beginning of a String
$ - End of a String
[] - Matches Characters in brackets
[^ ] - Matches Characters NOT in brackets
| - Either Or
( ) - Group
Quantifiers:
* - 0 or More
+ - 1 or More
? - 0 or One
{3} - Exact Number
{3,4} - Range of Numbers (Minimum, Maximum)
#### Sample Regexs ####
[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+