Warp Drive

A shipboard device which allows a spacecraft to travel at faster-than-light speeds. With sufficient energy, a warp drive bends space-time around itself to create a bubble where a ship can apparently break the lightspeed barrier. Also known as an Alcubierre drive to human-dominated societies. Though this would be accurately described as an inertialess drive, the term would also apply to other propulsion systems and is thus not the preferred naming convention.

Utility

A warp drive enables practical faster-than-light travel without the drawbacks of conventional, uncompensated relativistic movement. Given their immense power requirements, warp drives are normally mounted on ships with the appropriate power plants. This allows said ships to traverse galaxies, and eventually clusters or even superclusters, in reasonable periods of time. Warp travel is inertialess from the traveler's frame of reference, and a ship can accelerate as fast as it can ramp up power to its core.
Particularly advanced nations use warp drives in their electromagnetic accelerator munitions and torpedoes, making ranged FTL combat much more viable.
A particularly fast mass-production example is the strategic weapon known as the Maneuverable Intergalactic Superluminal Deterrence: at flank warp factor, a now-obsolete Block 25 starcracker could sustain a speed well over 500,000 light-years a second.

Access & Availability

While not a particularly difficult concept for any species which has brushed with theoretical physics, actual implementation can be full of stumbling blocks for an FTL-aspiring civilization. Pretty common in the wider universe, as the dominant form of FTL travel.