. - matchs any character
[abc] - can match the letter a,b or c
[^abc] - can match letters with our a,b and c
\d - any digit ,short for [0,9]
\D - non digit ,short for [^0-9]
* - Occurs many times or 0 times it doesnot matter
+ - Must occur at least one times and can occur many times
? - Occurs one times or 0 time, Cannot occur multiple time
{x} - occurs x number of times.
\d{3} means seraches for three digits
{x,y} - Occurs in a range between x and y times
{3,4} - means it can occur 3 times , or 4 times . Can not occur more than 4 times