Why a laser? NASA says the radio spectrum it's traditionally relied on to transmit signals is getting increasingly overloaded with traffic. Capturing radio signals from space also requires gigantic sensors. Sending information as a laser is much more efficient, and will allow new capabilities like 3D video and other high-bandwidth applications. In addition to downloading data at tremendous rates, NASA also successfully tested uploading information via the Lunar Laser Communication Demonstration at a more stately 20 Mbps.
Eventually, this technology might help NASA stay in contact with very distant spacecraft. For now, I just wish they'd point the laser at my house.