I have been learning how to rope lately. Not because I need to, I don't even own cattle or anything else rope-able, but because I think it's fun, and it can give some variety to horse training.
The horse and rider learn a lot of things that I consider important for me, like remaining relaxed when there are noisy things swung overhead, or when surprisingly touched by stuff. Also there are coils in your one hand and the loop in your other, so you need the horse to be controlled off your legs and seat mostly.
Dallying is when the target has been caught, and the rope is wound around the saddle horn. Next step for us would be to have the horse move in a certain direction and make contact, i.e. put some pressure on the rope. Note that in ranch roping, the rope is not tight around the horn, but more coils can be "fed" into the rope such that a struggling animal can be slowly stopped, instead of being choked and jerked around hard.
At least that's the theory. For us it's catching the dummy.