Get it checked soon! - it's the warning light for the brakes and usually means that one circuit has a major leak or some other imbalance. This light looks like (!) with the ! inside a 0.
There is another similar one which means a bulb failure - it's similar to the one above but has radial arms from it and a small square on top.
So if it's the former get it checked soon.
Good Luck.
I was gonna say! Its brakes, not the handbrake lol. As hako said, its caused by a pressure imbalance between the front and rear circuit. So either a major fluid leak or one of the pistons within the master cylinder has failed.