First or second focal plane

In a first-focal-plane scope the reticle is magnified with the image, so its hash marks mean the same thing at every power. In a second-focal-plane scope the reticle stays one size and its marks are only correct at one magnification, usually the top. That is the whole difference, and it decides more than the glass does.

The long version: FFP vs SFP, which should you buy?

Only groups with two or more scopes get a page — one scope is not a comparison.