The Seven Minutes of Terror denotes the blackout time during entry into the Martian atmosphere to the time the probe finally gets a signal back to the JPL in California. It also refers to the revolutionary mode of landing. In the past they used rockets and air bags to soften the landing. This time they used what they called a sky crane. The crane itself is a craft that essentially hovers in midair and lowers its payload via tethers to the ground and then flies away to crash elsewhere instead of crushing the rover.
The rover is almost the size of a Mini Cooper and weighs about a ton. It dwarfs all previous Mars rovers. Its mission is to study the atmosphere and geology of Mars. It is being hailed as the first real step in putting human beings on the surface of another planet, even if that planet just looks like some parts of northern Arizona.