As stated in section IA of the wiki, each significant body possesses some gravitational attraction. For the most part, this gravity is not enough to serve as a gravitational field for anything except air pockets. However, sufficiently large bodies (such as, say, large vessels or kindori) can produce their own gravitational fields, as can various magical objects, such as certain spelljamming helms.
Gravitational fields, in this case, are planar along the major axis of the object providing the gravitational field (not isotropic as one might expect). Crewmembers on a vessel can thus walk on the underside of a spelljamming vessel in spaceflight without falling off. It is also possible, due to the planar nature of the gravitational field, for a crewmember to drop an object off the side of a vessel in wildspace, have the object fall for a short distance, and rebound back up to the person who dropped it.
It should be noted that the gravitational field of any body only extends as far as the air pocket it possesses—therefore, one is advised not to eject an object with too much force from the ship (unless said object is intended to be launched away).