It is a test launch, that will carry Tesla Red Roadster car from Musk's private collection, with a mannequin in new SpaceX astronaut space suit at a driver seat, to the Mars:
SpaceX wrote:When Falcon Heavy lifts off, it will be the most powerful operational rocket in the world by a factor of two. With the ability to lift into orbit nearly 64 metric tons (141,000 lb)---a mass greater than a 737 jetliner loaded with passengers, crew, luggage and fuel--Falcon Heavy can lift more than twice the payload of the next closest operational vehicle, the Delta IV Heavy, at one-third the cost. Falcon Heavy draws upon the proven heritage and reliability of Falcon 9.
Its first stage is composed of three Falcon 9 nine-engine cores whose 27 Merlin engines together generate more than 5 million pounds of thrust at liftoff, equal to approximately eighteen 747 aircraft. Only the Saturn V moon rocket, last flown in 1973, delivered more payload to orbit. Falcon Heavy was designed from the outset to carry humans into space and restores the possibility of flying missions with crew to the Moon or Mars.
Some more info on the rocket can be found THERE.
A small update. The Launch has been postponed, due to wind, till 20:45 (GMT/UTC+0). If the wind won't settle down to acceptable level the launch might be postponed till tomorrow.
Launch at 20:45 (GMT/UTC+0) was successful.