Is guerrilla the name of the people who fight in a war?
Yes, but only certain types of warfare. "Soldier" is the multi-purpose name for a warrior.
A guerrilla is a person who uses a particular type of warfare. They are generally a small band of a rebel faction engaging in war independently of their government, usually illegally (according to the Geneva Convention -- though I'm not sure how relevant that still is). Guerrillas hide among civilians, often do not wear uniforms, make surprise attacks and then retreat into civilian life again. They often have charismatic leaders and sometimes unusual ideologies.
Guerrilla has derived from spanish word Guerra which means to fight.
Gurerrilla in spanish means a raiding party.
Alternatively any member of such raiding party is also called a guerrilla.
In Military Science, a guerrilla force is an indigenous force which does not have regular army type organization and training. Except some basic training and low availability of advanced equipments, these guerrilla rely on the element of surpirse and hit where the security is least and run away after attacking to save themselves.