The acceleration of gravity toward any object depends on its mass
and your distance from its center.
In space, the size AND DIRECTION of 'g' depends on the masses
around you and your distance from the center of each one.
If there's one object ... like a planet or a star ... that's bigger than
any others and closer to you than any others, then you can ignore
the others and just calculate the acceleration of 'g' toward that one
object that drowns out the others.
Example:
If you're in space only a few hundred miles from the surface of the
Earth, like maybe on board the International Space Station, then the
'g' on you is practically all due to the Earth and the sun, and you can
ignore the effects of gravity pulling you toward Jupiter, toward the Moon,
and toward the space station itself.