The ping is the time needed for a packet of information to go to another computer and come back to yours.
It mainly depends of your connection quality, the other computer's connection quality, and the distance between them.
A good adsl connection will be a lot better than a bad one, or than a RTC connection.
There are a few things that can make your ping worst that it should be :
- be sure to turn off all your downloads (including P2P program)
- check your PC doesn't have virus ( free anti-virus : www.avast.com
) or spyware ( free anti-spyware: www.spybot.info
A bit more information on the Wikipedia :