What were smoke screen actually I read so much about them in WW2?

Question

Smoke unit, howitzers, mortar units etc?

Answer 1

It was actually smoke used by combatants to conceal the maneuvers of troops. The concealed soldiers changed positions while under cover of the smoke. The smoke was generated by machines.

Answer 2

Ships like PT boats, Destroyer Escorts, and Destroyers were built with Canisters that would give the ship the ability to plum smoke behind it. It was dumping oil onto the engine. The ships of WWII can't make smoke because of the fuel. Coal was the fuel to always have a smoke plume. Oil was a cleaner burning fuel, it left no smoke to be easily observed.