An insurgency is a violent, armed rebellion by small, lightly armed bands who practice guerrilla warfare against a larger authority. The key descriptive feature of insurgency is its asymmetric nature: small irregular forces face a large, well-equipped, regular military force state adversary. Due to this asymmetry, insurgents avoid large-scale direct battles, opting instead to blend in with the civilian population where they gradually expand territorial control and military forces. Insurgency frequently hinges on control of and collaboration with local populations.

Rebellion is a violent uprising against one's government. A rebel is a person who engages in a rebellion. A rebel group is a consciously coordinated group that seeks to gain political control over an entire state or a portion of a state.