You got that error because the socket is already in use. That means your apache tried to bind to port 80 and there was another application using it. Perhaps your distro came with a pre-installed http server...and that is more and more the norm so it doesn't surprise me that you get that error.
So far you are going in the right direction...trying to get started with Linux is perhaps the coolest IT experience that you'll ever have...even though it is full of these: ????
But the reward is well worth it!
Going back to your issue you can do 2 things:
1) Kill the process running on port 80 and start your web server again.
2) Make apache listen to another port, like 81 or 7777 or whatever you like....just remember any port under 1024 requires root privileges.
If you do start apache on port 81, remember that you will need to access it via your browser this way:
http://localhost:81
Cheers, and I hope this helped :-)