system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what is the equivalent for cardinal points North, south, east, and weast in space?
gpt
As others have said, you have to have a reference point.
Now, in orbit, there are some directions that are used for navigation, but they're dependent on your particular orbit. 
Still, they're handy to have if you ever find yourself in an orbiting space hotel and want to impress that cute tourist :)

They are:

* Prograde: Your direction of motion relative to the thing you're orbiting. If you think of the orbit as a roller coaster track, you're looking directly forward. This is the direction you want to accelerate to raise your orbit. 

* Retrograde: The opposite - looking directly backward. This is the direction you want to accelerate if you want to lower your orbit or re-enter the atmosphere.

* Normal: In an equatorial west-to-east orbit, this would point north. In an inclined orbit, it'd be north-ish. It's 90 degrees from the prograde/retrograde line, parallel to the planet surface. If  you could move in this direction without disturbing your imaginary roller coaster track, the track would seem to curve to the left, with your orbital path going counterclockwise. This stuff's hard to describe without pictures :) If you look in this direction, you'll see the horizon of the earth, with the ground moving from right to left beneath you.

* Antinormal: 180 degrees away in the other direction. Again, if you're in a perfectly un-inclined orbit at the equator, this would point "south." You'd be looking at the southern horizon and the earth would seem to be moving left to right beneath you.

* Zenith: Straight away from the planet surface. Closest thing to "up".

* Nadir: Directly toward the planet surface. "Down".