Yes a*b* -- Regular one ( It can take any number of a and b )
anbn ---- An equal no of a and equal no of b
The regular lang is accepted By a Finite state Automata . It doesnt have any memory with it .
So for the first one it doesnt have any restriction to keep track how much a and how much b it has read . it wouldnt have restriction of a, b, aaabbbbbb, abbbb,bbbbb , aabb etc
While for the second , if it has read 3 a then it should read 3 b also , but FA doesnt have memory only , it read 3 a and then when it start reading b , it doesnt have any idea about how much a it read .
Hence the second one is non regular :)
I hope it help you !