Faster-than-light travel refers to the purported ability or potential to break the universal speed limit of light. The speed of light is exactly 299,792,458 meters per second (the meter actually defined by the speed of light), but is usually known as 3 * 10^8 meters per second. Although this is the speed of light in a vacuum and the speed of light is affected by the material through which it passes, the speed of light under any given circumstance is the maximum possible speed at that circumstance.
Some claim that this fundamental constant of the universe can be broken. But the amount of energy it takes to accelerate an object with rest mass rises sharply as c is approached until a discontinuity is reached. It would require infinite energy to cross the final gap. Additionally, local time slows dramatically as velocity nears c in a phenomenon called time dilation. At exactly the speed of light (assuming an object with rest mass could attain it, which it cannot), local time stops altogether.
Possibility of Travel Faster than the Speed of Light
Einstein's theory of general relativity does not rule out the existence of shortcuts in space-time called wormholes which could permit the travel of a ship from one part of the galaxy to the other, bypassing the intervening interstellar space. An extraordinarily advanced civilization could conceivably construct artificial wormholes connecting a group of stars like a subway system. Carl Sagan described such a network in his novel Contact.