To launch something is to propel it or get it going, usually from a standing position. You can launch a rocket, a career, a product or even a watermelon. Either way, you're getting it off the ground.
Launch often means to start something, but to start it in a big way: "The launch of the shuttle was also the launch of a new era in space travel." Time was, when a singer finished making her record, the company would simply "release it." Eventually, though, that wasn't enough. Now a record needs "a launch" — a full-scale media blitz to get people excited enough to buy it.