Photo / Video
IBIS (in-body image stabilization)
The camera's sensor physically shifts to cancel handshake, steadying any lens you mount.
A mechanism that physically moves the sensor to counteract small camera movements, stabilizing whatever lens you mount — including older or manual lenses that have no stabilization of their own. In practice this lets you shoot sharper handheld stills at slower shutter speeds than you otherwise could, and it smooths out handheld video.
Spec range
makers usually quote the benefit in 'stops' of stabilization (often in the region of 5–8 stops), where more stops means you can use a correspondingly slower shutter. Concrete example: IBIS can let you hand-hold a shot that would normally need a tripod or a much higher ISO.
What it means when you're buying
IBIS is most valuable if you shoot a lot handheld, in low light, or with lenses that lack their own stabilization.