I took a class on "Terrorism and guerrilla warfare, believe it or not. There are differences. Guerrilla warfare is the term for a war strategy that involves small, fairly unorganized bands of “guerrillas” (warriors) that use distinctive tactics (like ambush, small raids) to fight their battles. The patriots of the revolutionary war are a prime example. Compare them to the highly organized British army. They have neither the numbers, the organization, nor the equipment to attempt a full frontal assault. Rather they come from behind and the sides, constantly pecking, pecking, pecking at the infrastructure, hoping to eventually cripple the opposition. Or wear them down so that they just want to pack up their bags and go home.
A key component of guerrilla warfare is the ability of the guerrillas to “swim in the sea of the people.” In other words, since they aren’t wearing uniforms and marching around and beating drums, it’s hard for the enemy to distinguish civilian from foe. Guerrillas may even pretend to “cooperate” with the opposition as a mask. Guerrilla warfare tactics are usually employed by natives on their home terrain. They are at a great advantage by knowing the geography, weather, hiding places, etc. (think Vietnam). Guerrilla tactics are usually deployed in a defensive situation (e.g. against invaders.
Terrorists, on the other hand, are not trying to conceal their agenda. They use violence as a means to promote fear and disrest which they hope will further their political cause. They usually always follow an attack with a “statement” explaining their agenda. Terrorism is offensive and is usually highly organized, with one or two recognized “leaders” or strategists. Publicity is a key component of their strategy. They are usually fighting for a “cause” versus land, though not always.