I think a furnace would refer to forced hot-air heat, with the furnace being the thing that heats the air being blown around through the vents.

Boiler would be to heat water/steam for radiant heat.

I am wondering what other appliances would be covered. What about electrical work or plumbing? Even if you don't do the work yourself, knowing a bit about what's involved can help avoid getting ripped off.

I'm regularly shocked by people who are incapable of doing basic home repairs.