Metacharacters
Metacharacters in regular expressions are called all these weird special characters to regex that mean something specifically to a pattern and cannot be taken as a letter literal.
We place them always between the two backslashes where we define the body of our pattern. Some of the most common used include:
\w Which matches any letter or number. It is called word character
\d which matches all digits(numbers)
\s matches a space character
\. matches all letters, digits and special characters (be careful with that!)
\D all non-digit characters
\W matches all non-word characters (everything that is not a letter nor digit)
