What is the difference between a lance and wand?
A lance is the metal pipe piece between the gun and the spray nozzle. A wand is normally considered the assembly of the gun, lance, and couplers.
What is the difference between a "trigger gun" and regular spray gun?
Nothing. Trigger gun is just another term for a pressure washer spray gun.
Should I burn kerosene or Diesel in my BE forced air space heater?
The short answer: either, take your pick, but choose grade #1. Personally I'd pick grade #1 (K-1) clear kerosene, it's the cleanest, less soot and smell.
The long answer: Kerosene and diesel are very similar. Both come in a couple grades. Grade #1 Kerosene is similar to grade #1 Diesel and JP8 (jet fuel) - the biggest difference is additives. Grade #2 kerosene, grade #2 Diesel, and furnace oil are similar to each other too. The grade #2 products are 'dirtier'. BTU heating values depend on fuel grade and type.