can smoneone please tell me because i dont no wether to buy or not and what is an avitar

Okay.
When you open game, first that you have see is window with menu. GUI textures will give you the way to costumize your window.

what ?

that

were do i click to customize ?

When you get the item you would click on it from your inventory and there will be a menu where you can upload an image.
From there you can upload a picture and when you activate that item your menu will have that image.

The background imageThe title of the menu screenthe toribash iconthe image behing the menu (back layer)

Also click on the pictures to get a link to them in torishop.

an Avatar can be an item in-game or the one you see in forums under our names.
You can go here to upload your avatar in forums.

The avatar in-game is the one you see under you belt rank. It is your miniature of your head that is spinning. But before you can use that, you need to have this item and activate it.

Yes, the Logo and Header allow you to edit your main menu.
Here is an example.
Hampa's I believe.