The minimum requirement when fitting a front frame system (unless you're making your own plans), is that you include a shelf to support the door frames against the back wall. The front frame shelving comes in long lengths, which you will cut to size, and includes an aluminium support for the wall, and a support panel for the front of the shelf, all of which can be cut to size during installation.
The front frame top is actually the same as the front frame shelf, and is an optional extra. It is used to create a top to your front frame system, although in many cases you will prefer to use a simple infill panel between doors and ceiling, so that you have floor to ceiling storage inside your wardrobe. Available in 1.2m and 2.4m lengths.