I dont know how to forward port 80

[Micah James Sergey <earsofdeath@xxxxxxxxx>]

hello, i have my computer hooked up through a router and would like to 
use my computer as a server. ive set up the router so it forwards port 
80 to the to-be server. however, i have no idea how to set up the 
iptables so the server accepts stuff. id really appreciate it if someone 
would send me the commands for doing so. it'd also be nice if they could 
explain what each line does.