dmof wroteFrom my understanding the ET is the offset of the wheel. The number that comes after ET ex. ET40 is referring to how far the wheel sticks out past the centre point, if you know what i mean
If a wheel had an ET of 0 then the face of the wheel would be flat. If a wheel had an ET of say 70, it'd be quite concave. If the offset was minus like ET-20 it'd be pretty weird and be convex.
The numbers 7.5", 8.5" and 9.5" refer to the width of the wheel. If you want quite wide wheels then 9.5j would be what you're looking for.
If I was you I'd go for the last set of wheels in the picture. To me, they are the best looking wheels out of the lot. They kind of look like directionals but different. Quite nice on any sort of German car i.e. BMW, Audi, VW etc.
The fitment of most German cars is 5x112 I believe so don't stress too much about that. You can make sure that the fitment is 5x112 pretty easily by just Googling it. A Google search like "mk6 golf 1.9tdi wheel fitment" will bring up most of the details that you will require when it comes to your wheels.
Hope this info helps you out a bit
Really appreciate all the help man, just sort of overwhelming with all the different numbers but once you broke it down for me its a lot easier to understand. Now i'm just stuck on choosing silver, black or white wheels. My golf at the moment is all blacked out but i was thinking of maybe in the near future getting it wrapped in white while leaving certain parts black such as the mirrors, roof and spoiler, not sure yet.
If your car is already blacked out, go silver, white, or gold/bronze. If you go black wheels on an already blacked out car, you'll look like everyone else. This is just my opinion though.
I have a platinum gray Jetta MK6 with silver 17x8 TSW sebrings. With black trim everywhere else. I get compliments all the time.
Good luck with the car!