Apache Question Please Help

What is the whole purpose of Apache?
All I would like to do is access the internet. Someone on this board said all I had to do was plug in the cable from the cable modem into my G3 iMac and set up. I opened Internet Explorer, typed my IP Address in the URL bar and it opened up with Apache. I have no clue or idea what the heck this is. I just want to access the internet (I.E. google.com, msn.com and use AIM) Please help, I just want to access the internet. Thanks.