A combination of the special characters, enclosed by a pair of slashes (//), makes up a regular expression pattern.
^ Matches the beginning of a line
$ Matches the end of a line
\w Matches a word character
[...] Matches any character in the brackets
[^...] Matches any characters not in the brackets
* Matches zero or more occurrences of the previous regexp
+ Matches one or more occurrences of the previous regexp
? Matches zero or one occurrences of the previous regexp