Rake/ offset is the difference between the centerline of the steering axis, and the center of the hub axle.

BUT that is only PART of the steering Geometry.
with the steering axis being at an angle,
the vertical line thru the axle crosses
the angled line of the steering above the ground-plane
so on the ground the tire touches the ground behind the steering axis line..
that is TRAIL.

trail is reduced as the rake is increased, reducing rake, increases trail

because the 2 lines cross

someone elsewhere on this site has graphics showing this

a+b=c but only if you don't change a, or b to another value..