Regular Expression: +$ VS *$ VS none

Question

In regular expressions, what is the difference between ^[a-zA-Z]+$ and ^[a-zA-Z]*$. Also would I be able to not include it at all, either with ^[

Answer 1

+ means 1 or more * means 0 or more

So an empty string is found by ^[a-zA-Z]*$, but not by ^[a-zA-Z]+$

^[a-zA-Z]$ means EXACTLY one letter in the ranges a-z and A-Z.

a+ is a, aa, aaa, ..., aaa...aaa, etc

a* is an empty string, a, aa, aaa, ..., aaa...aaa, etc

^a$ is only a

EDIT: you can also use ^a?$ to find 0 or 1 occurence of a, so either an empty string or a