My use case is that i use my other computer primarily for watching TV (my notebook overpowers it and i use it with dual screen at home). So, usually i don't need a full blown KDE, but only kdetv as i have an older analog TV card plugged in. Thus, best is to generate a kdetv-only session.
Therefore you need basically two files. The first is .desktop file that populates your session, the second is the script which is being started if you log into it. Let's take a closer look: