Glossary
Smoke
In one line: An ability that creates a cloud blocking vision, to cover a passage or an angle.
What it means
A smoke is a sphere or wall you cannot see through. It is the most important utility in the game: it lets attackers cross a choke unseen and lets defenders slow down whoever is coming in. Controllers throw most of them, but other agents have some too.
The right smoke blocks one specific line of fire: the one the enemy is watching from. A bad smoke covers the wrong space or blocks your own team's view. Smokes do not last long: throw them too early and you walk in after they are gone.
An example
A site is watched from a high window. The controller smokes off the window: now whoever enters does not have to worry about that angle and can focus on the others.