As I still am a beginner I have had just the same questions you do.
I desided to ignore them as I started off with the first
tutorials (photoshop isn't easy to start with, but with this help I'm learning fast)
Then I wondered what else was in store!
The
elements I found pretty basic (shapes etc. that you can paste on your layout). To make them yourself is something entirely different.
Filters are programs within the program to do something. (see below)
Textures (pictures that have some kind of texture in them like briks) are handy to give your grafics a 'real' look (in photoshop there is a standard filter called texturiser that you can use any texture (picture) with.
You can also make your own backgrounds from your photo's with the filter patternmaker.
Brushes can be made yourself (something for later)
If you use your paintbrush (in most programs) you can choose what kind of shape this brush actually is. These sizes etc. are called brushes.
You can also download brushsets from different sites.
In my case (photoshop) on allmost every topic there were a ton of
tutorials to follow

on this site and
www.escrappers.com were plenty
Sometimes the search for the topic was started by a thread about brushes for example.
My advise don't overdo it!
Try the easy stuff first and see what great things you can do with that.
If you figure something out use that a few times before you start on something new (otherwise you'll forget like I did LOL)
If you are ready for something and can't find it on your own, ask around like you do now.
I'm looking forward to your first layouts