Skilled hacker knows what do to and how to do. He makes his own scripts and codes which he uses for hacking. He knows where to exploit the script and where to attack whereas, an unskilled hacker isn't an expert in programming languages, codes, etc.
A skilled hacker is a pro in programming languages, codes etc. whereas, an unskilled hacker doesn't know what to do.
An unskilled hacker uses the scripts and codes of skilled hacker. He has to face failure more often then a skilled hacker.