Well, I created a phpBB website into my XAMPP web server running on localhost, my computer, and my computer is the only place I can access the forum. How would I be able to access it on another computer on my Local Area Network. Maybe you understand, maybe not but I'm just fooling around with web servers and eventually I wanna create a "Live" website that is completely free using my own hosting a a free domain name. Any help on this is appreciated.
You have to make sure the server is configured to listen on both your loopback IP and your LAN IP. You also have to make sure you don't have a firewall blocking port 80. Then, you need to go into your router configuration (or modem if applicable) and forward TCP port 80 to your computer's LAN IP. Also, your ISP has to have port 80 unblocked. Some ISPs block port 80 to prevent you from hosting websites on it.
Side note: I don't suggest hosting websites on your own connection because most residential internet connections don't have enough upload bandwidth to server a decent amount of users. It also isn't as reliable as having your site hosted in a datacenter. You'll also have issues if your IP address changes. Even if you use a free service to keep your subdomain up to date, there will still be downtime during the change over. And last, but not least, your site will be down each time you restart your computer or if it's accidentally shut off. But if you're just doing this to mess around, then go for it.