Superdrives allow Earth Empire ships to travel up to 10x the speed of light. They are installed on all Empire ships, but can only be used at maximum power in an emergency.
The maximum speed allowed by Empire regulations is Warp 6, at 6x the speed of light, mainly to stop ships from going too fast.
The difference between superdrives and hyperdrives
Superdrives allow only up to 10x the speed of light, whereas hyperdrives, still being experimental, can allow 15x, or with minute adjustments 20x, the speed of light.
Pretty damn fast, don't you think...sir?—Meatbag to Zero
Hyperdrives and superdrives were derived from the discovery of the Earth-Link.