In Chapter 3, Nate and Victor Sullivan activate explosive charges around Lazarević's camp. The charge glows green when it is unactive and safe to be around, but once activated it changes to red to indicate that it is armed and dangerous to be around.
In Chapter 2 of the co-op adventure missions, Charlie Cutter uses an explosive charge on a wall blocking the party's path. The explosive does not trigger straight away, however, rather detonating while the trio are halfway through the gap.
The weapon cannot be freely used by the player in singleplayer or multiplayer.
The explosive charge appears to be C4. A powerful plastic explosive used by the military and demolition crews.