In Counter-Strike, the bomb carried by the Terrorist team is called the C4.
The C4 is the objective item in bomb-defusal missions. Terrorists attempt to carry it to one of the designated bombsites, plant it, and protect it until it explodes. Counter-Terrorists try to stop the plant, eliminate the attackers, or defuse the device.
At the start of a round, one Terrorist receives the bomb. That player can pass it to a teammate or drop it, allowing another player to collect it. The bomb carrier is marked for teammates, which helps coordinate movement and attacks.
Counter-Strike uses the familiar C4 designation from real-world explosive terminology, but the game’s device is a fictional gameplay object. It is not a simulation of a particular real bomb model.