Mine is First Focal Plane (FFP). The reticle grows and shrinks as you change the zoom.
Second Focal Plane (SFP) is the one you see more often. It is cheaper than FFP, and the reticle is always the same, no matter what you set the zoom to. Also, if you are using an SFP scope to range a target using it's MIL or MOA grid, you always have to set the scope to the power where the mil-dots are accurate (usually the highest power).
With an FFP scope like the one I got, the mil-dots are always accurate, at any zoom setting, because those mil-dots zoom in and out as you change power settings.
Most people do not need an FFP scope. But for long range, FFP is better, because you are not always using the max power (where most SFP scopes are calibrated). So if you're holding off, say 2 mils for wind, then you can zoom your scope in and out and you have that 2mils mark always accurate for wind hold off no matter what power you're at. You might think you mostly use the highest power for long range shooting, but that is apparently not the case. I am just learning this stuff. At long range you get a lot of mirage in the scope. To "fix" that, you move to a lower power. But on an SFP scope, moving to that lower power just nuked your ability to hold off for wind, since your mil-dots are no longer accurate.
With an FFP scope for long range, the reticle is thin at high powers so it doesn't blot out your target. But since the reticle gets smaller as you zoom to lower powers, the reticle gets thinner and thinner too. I mean, REALLY thin. You can see it from a supported position on a bench or with a bipod, but it would be terrible for hunting because the reticle would just disappear at low powers. That's why hunters don't typically use FFP scopes (except maybe long range hunters).
I learned a lot about how to choose an appropriate scope in my research. A fantastic hunting scope could be total trash for long range shooting, and vica versa. Also with long range, you have to have turrets that are extremely consistent and repeatable. If you dial in 13.2 mils, you darn well better get exactly 13.2 mils. And then when you dial back to zero, you better be at the exact same zero as when you started. Most hunters use the turrets to zero their scopes, and then leave them there. Not touching them again until they decide to re-zero the scope. This is not the case for long range hunters, since they have the same concerns as long range target shooters.
Good glass is very important in any scope. But arguably, the turrets are even more important in long range scopes.
