"James L" wrote...

How does it relieve the pressure on the tiller? I do notice a strong force
on the tiller when there is some wind. I don't remember this on the Topper
that I used to sail earlier.

A properly rigged boat will be "balanced" when the sails are trimmed on most
points of sail. In this context, "balanced" means you need little or no tiller
pressure to maintain a straight course. Most boats are rigged with a little
"weather helm" -- the tendency to turn into the wind -- when the tiller is
released. This gives a bit of safety factor, so the boat won't run downwind out
of control if you temporarily lose control of the tiller.

With a jib and main, you can fine-tune the rig balance. Tightening the jib a
bit more (relative to the main) will create more downwind force on the bow,
causing a "lee helm" -- turning away from the wind -- tendency. Easing the jib
relative to the main will reduce the jib's effectiveness slightly, giving more
weather helm.

Finally, when running dead downwind, the jib can be set on the opposite side of
the boat from the main, called "wing and wing." The boat's tendency to turn
into the wind will be much reduced, and the power of the jib will be much more
effective.