Hi mate
In a nutshell, I machine polish out swirl marks, scuffs, scratches, brighten dull or oxidised paint, seal and/or wax to then keep that nicely corrected paintwork looking lovely.
In terms of cars specifically, I clean and condition leather interiors, or just clean fabric ones, carpets, all plastics - I can kind of go as crazy as someone wants to be honest. The Lotus Carlton I literally cleaned everything from top to bottom, including dust of out switches, vents, etc.
Wheels, metals bits polished to remove tarnish marks, etc.
The whole lot to be honest!
Most of the time, people just want the paintwork side of things done - and not even down to removing every swirl mark (which to be honest I would always suggest is a bit of waste of time anyway, seeing as swirls will be back in no time anyway) - so I tend to get out noticealbe marks and generally bring the car back to 'as new' looking, which is what people want the vast majority of the time anyway.
It's just a hobby/passtime for me anyway, I have a full time job which is far less interesting unfortunately.