By definition, travel between bodies in a given star system. For our solar system, the velocities involved are significantly higher than those needed for orbital maneuvers, and conventional rockets are for the most part inadequate for interplanetary craft. As a result, most interplanetary travel makes use of gravitational slingshot effects to effect velocity changes and gain speed. A prime example of this are the voyager spacecraft, which used slingshot effects to change trajectories several times in the outer solar system.
While manned interplanetary travel has not yet been achieved, a trip to Mars is quite feasible with present technologies and could probably be achieved within a decade (at most two) if the funds were made available. NASA's "Design Reference Mission" proposes a Mars exploration program costing $50 billion.