Phasers are fictional energy-based weapons commonly featured in the Star Trek universe. They can be set to different power levels, allowing them to stun or kill targets. Phasers are typically depicted as handheld devices, but larger versions exist for starship use. In the Star Trek series, phasers are used by Starfleet personnel for self-defense and combat situations. They emit a beam of energy that can be adjusted for various effects, making them versatile tools in both exploration and conflict. The design and functionality of phasers have become iconic in science fiction.