Warp drive derives its name from the fact that it warps space and/or time, allowing for faster-than-light travel without the need of faster-than-light movement. The Alcubierre drive is a proposed example of this, distorting space ahead and behind the ship so that it crosses a greater distance during forward travel.
More than any other sort of FTL system, the warp drive is easily scalable. If you want a faster ship, just put more warp drive in it! It doesn't require the ship to enter into another continuum, which means that the ship can interact with the normal universe. But warp drives are easily the heaviest, most expensive, and most power-hungry, drives available.
Warp drives require two tonnes of “warp core” to be installed; this is a control component, and generates no warp thrust. After that, every 20 kilograms of warp drive delivers one tonne of warp thrust. Warp drives occupy one cubic meter per 750 kilograms of warp drive, including the core, but this includes the space required to repair the drive. Unlike other FTL systems, warp drives cannot be installed externally!
Warp drives are extremely expensive, at ₠225 per kilogram.
A warp drive is a power hog, requiring 120 kW of power per tonne of warp thrust.
If your setting uses an exotic fuel for its warp drive, that fuel will provide 168 tonne/hours of thrust per kilogram. Or to put in another way, if one kilogram of fuel is installed for every tonne of warp thrust delivered, the fuel will last for one week.
“We can't go any faster than warp 5, Captain. The engines can't take it.” – Hikaru Sulu, The Slaver Weapon
To determine your spacecraft's warp speed, divide its warp thrust by its mass. This gives you its speed in parsecs per week.