A generator is a base asset that powers other base assets. They are often located at the heart of a base. They can sustain a decent amount of damage and are often targeted by heavy offense and other attackers.
Destroying a Generator
The best way to destroy a generator in most mods is by using a mortar. In base, one shot will disable it. In classic mod, throwing a hand grenade and mine together while hitting the generator with mortar will disable it.
If you don't have heavy armor, the best way to take out a generator is by using a gd. Combine hand grenades as you see fit.
If you need to take out a generator and have no access to equipment, the best tactic is to combine your hand grenades with your chaingun to take it out. This form of attack is almost completely the realm of Siege, when attacking undefended generators such as the North Forcefield Generators on Ultima Thule.