Left hand side buttons:
Volume increase and decrease.
The star button mutes the audio or it can activate voice dialling (I think) if you have the Skoda bluetooth kit installed.
The phone button doesn't do anything unless you have the factory fit phone kit with a cradle.
Right hand side buttons:
The top button scrolls through all the different menus in the MFD.
The arrows scroll through the MFD, take you through the different options in the menus, change music tracks, changes radio stations, etc.
The ok button selects the option you want to change and then confirms it, answers/ends the call with the Skoda bluetooth kit.
I can't remember what the buttons do if you have the satnav installed as haven't used mine for a while.
HTH.