Artificial gravity refers to the simulation or creation of gravity, generally to simulate the effects of being on the surface of a planet for various purposes, most notably for the convenience of living beings that evolved to live in such enviroments (such as Humans). In real life, the methods available to simulate gravity are the inertia of an accelerating vehicle and centripetal force.
Artificial Gravity in Science Fiction
In science fiction, futuristic technology is often able to create artificial gravity by literally generating gravitons. In addition to keeping stuff on the floor aboard spacecraft, this technology may be used for tractor beams.
In Mass Effect, the titular mass effect technology allows control of mass and gravitational fields. It's a foundational technology for most of the futuristic equipment and an important plot device, as well.