Oh are there different types? So except for the current GT-R, has the skyline always just been a model in the range (like the IS for example) with different variations in spec and power?
Yeah the Skyline was basically a boring old JDM saloon car. The GT-R came out properly in 1989 (ok yes, if you're a GT-R anorak then I know there was one briefly in Japan in the 70s) with the R32 model, with the twin turbos and 4WD. So yes, there are different variants with different engines/capacities, and normally aspirated/turbo/twin turbo.
The R33 and R34 had GT-R variants too. But the R35 onwards are back to less glamorous saloons again, no GT-R. Instead now the GT-R is a separate model, not a Skyline at all, i.e. this one :