This is not meant as an exhaustive reference on regular expressions, but just something that may be helpful if you get a little stuck. I hope you find it helpful.
1. What kind of character is it?
[] - any of the characters inside the brackets will match
(use the dash to indicate a range)
Examples: [a-z] will match any letter.
[aeiou] will match any vowel
\w - "word" characters. Basically matches [a-z0-9_]
\s - "whitespace" characters. matches spaces, tabs, etc.
\d - any digit. Basically matches [0-9]
\t - a tab character
. - any character
2. How many characters?
(the below appear after the character class)
{x} - matches x number of characters
{x, y} - matches minimum x number of characters, maximum y characters
Examples: \d{4} matches 4 digits
* - matches ZERO or more of the character (as many as possible)
+ - matches ONE or more of the character (as many as possible)
*? - matches ZERO or more characters (as few as possible)
+? - matches ONE or more characters (as few as possible)
3. Where is the character?
\b - matches a word boundary, without actually absorbing any characters
^ - matches the beginning of a string
$ - matches the end of a string
4. Grouping
() - any characters between the parentheses will be their own group
(try checking the value of $matches after using -match)
| - a pipe character is the OR character
Example: (one|two) will match the word "one" or the word "two"
