Okay, so you know how sometimes when you use the internet, you see really cool things like games or animations that look like they are not just a regular website? That's what we call RIA, or Rich Internet Applications.
Think of it like this: imagine you have a box of toys. Some of the toys are just normal toys, like blocks or dolls, but some of the toys are really cool and special. Those are the RIA toys - they do special things that the normal toys don't.
Now, when you use the internet, you're usually just clicking on links and going from one website to another. That's like playing with the normal toys in your box. But when you use a RIA, you get to use the special toys - you get to play with things like interactive maps or games that you can actually play right on the website.
So basically, RIA is just a fancy way of saying that some websites have really cool and special things that you can do on them instead of just looking at words and pictures.