The distance between these two points is the trail. If the axle center trails the steering axis the trail is positive if the axle center leads the trail is negative. Positive trail helps make the steering self-center. A motorcycle has positive rake, as well, which up to approximately 45 degrees uses the weight of the bike to orient the axle center in a trailing position to the steering axis. This eliminates the need to push the motorcycle forward to effect that orientation, as in the caster wheel.
Most vintage bikes have trail in the range of three to four and one half inches.
Most street bikes are set up with fairly slow heavy steering and a strong rearward weight bias. This method has the added benefit of shifting weight to the front wheel. Another word of caution though, a little at a time. I never move fork tubes more than 5 mm at a time and usually only 1 or 2. Changing the frame attitude to reduce the rake also reduces the trail but there are a number of ways to reduce trail without affecting rake.