What I am assuming is that your integrated video takes over when your system doesn't have a video workload, and essentially puts your GTX 880M on standby. Once you start up a game, it should kick on. This saves energy, resulting in longer battery lifetime and less heat.
Install EVGA PrecisionX and monitor your clock frequencies of your 880M. Boot up a game and see if they change. It should switch over and boost clock frequencies of your card as well.