Due to so much less examples of regular expression on internet.. i have lots of confusion in regular expression.
[ab] what is the meaning of it in regular expression
it it a,b or its like a,b,aa,bb,aaa,bbb............
and
[0-9] is it like 0,1,2,3,4,5,6,7,8,9 only ?? or 0,1,2,3,4,5,6,7,8,9 ,10,11,12....
and what is the meaning of ^ and $ in regular expression??