Concealed carry is the practice of wearing a weapon that is not in plain sight. The concern is that if there is a confrontation between two individuals, it will not escalate if each party knows that the other is carrying a lethal weapon. The counter-argument is that if a weapon is in plain site in an environment where few people wear weapons, then that person may be singled out for attack.
Most states of the USA allow citizens to carry concealed weapons (usually a handgun), providing they have a legal permit to do so. This concealed weapon permit is abbreviated as a CWL, CCL, CWP, or CCP depending on the state. People who do not have a concealed carry must carry their weapons in a visible manner.