"Phaser" is an acronym for PHASed Energy Rectification. All phasers fire particle beams. Personal phasers can stun or kill an enemy. The stun setting can also be used for crowd control. Ship-mounted phasers can damage shields or other systems or even cut a vessel's hull.
Phasers are based on the rapid nadion effect, whereby energy is passed through a special phaser crystal resulting in a discharge of short-lived nadion particles (often the detection of nadion discharges is a key sign that a battle has recently taken place).
Nadion particles have varying effects on the subatomic bonds of particles with which they interact, largely depending on the mass of the atom in question. To wit, dense starship hulls are more resistant to nadion discharges than are humanoid lifeforms.
The disruptive effects of nadion discharges can be moderated to produce varying effects (discussed below), ranging from benign to extremely destructive. Phasers, as particle beams, travel below the speed of light, seemingly varying according to the scale of their emitter.
Phasers can be made to overload, either deliberately or by sabotage. One possible method to overload a phaser involves disengaging the safeties that normally manages the phaser's power system. This allows energy to be transferred from the power cell to the prefire chamber then back into the power cell faster than the cell can reabsorb the energy, causing the cell to overload. Phasers in the process of overloading emit a distinctive high-pitched whine. About sixty seconds after the overload started, the weapon would expend all of its remaining energy in an explosion capable of doing considerable damage to its surroundings