Just like yesterday, well, pretty much a few hours ago, I guessed that they were used for stuff like forums and registration-like stuff. Am I right? How do you use them???

Yep. Databases... as the name suggests, are used to save 'data' (organised information) in them.

Forums are an excellent working example of how you can utilize a database.

Basically we use 3 things :

1. HTML
2. PHP
3. MySQL

You see *this* HTML page. You type and create a post. Now when you "Submit" the post, the post's content goes to the web server. There PHP processes the data, and asks MySQL to store it in appropriate tables. (Read this post to know the basic terminology).

Simple. Now when another user browses the same page, PHP asks the MySQL to 'fetch' your post, and then display it using HTML.

Oh, I get it. So people use these MySQL databases instead of making their own, in say, C or even something simple like VB.NET? It's a good thing I'm in web design and not programming, hahaha

Even with VB.NET you have to use a database to store your data. (if any).
With VisualBasic.NET, I use either Oracle, or MS Access to store / access data.

And if you have a good capable machine, 'MS SQL Server' can be deployed too,
for use in conjunction with VB.NET to store our data.

Note: I haven't tried using MS SQL server with VB.NET till now!

Yeah, I knew about the VB and Access/Oracle thing. So people just use MySQL because it works with PHP, hmm? Interesting... well, here's another two things I'm going to have to teach myself.

MySQL used to be just one of affordable database servers. But, now, Sun, one of IT giants acquired it, so in the coming months, it'll be promoted as an enterprise database. Good database to learn. Knowing how to manage this will become a very marketable skill.