Variable speed of light is a cosmological theory about how the Universe became mostly uniform at the large scale despite fast expansion. That explanation is that the speed of light were much faster just after Big Bang than it is today, allowing it to redistribute evenly. The theory predicts the existence of filaments and regions in the Universe where the higher speed of light still applies, which in that case can be used as cosmic shortcuts.
Variable speed of light is not the same thing as warp drive, although both can be used to circumvent the light speed limit.
This is an article about space.