Let's look at some basic examples of regular expressions:
ab*c
This will match a, followed by zero or more b, followed by c.
ab+c
This will match a followed by one or more b, followed by c.
ab?c
This will match a followed by zero or one b, followed by c. Thus, it will match both abc or ac.
^abc$
This will match abc in a line, and the line must not have anything other than the string abc due to the use of the start and end anchors on either side of the regex.
a(bc)*z
This will match a, followed by zero or more occurrences of the string bc, followed by z. Thus, it will match the following strings: az, abcz, abcbcz, abcbcbcz, and so on.
ab{1,3}c
This will match a, followed by one to three occurrences ...
