system
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human
ELI5, do we have any system of "direction" in outer space?

With everything moving and no obvious cardinal directions, how do we tell which way is which? Is everything just relative to what it orbits? With the message on voyager giving our "address" would other planets even know which way to go?
gpt
Let's just talk about navigating within the solar system.

First, you have an easy direction - towards or away from the sun.

Second, you pick a couple of fixed points in the sky, really bright stars that you can easily identify.

With those 3 points you can determine your position anywhere in 3D space around the sun.  This is how spaceships beyond Earth navigate in deep space.

Traveling between the earth and the moon, the Apollo astronauts used star sightings and known landmarks on earth (like Cuba, Hawaii, Baja California, Madagascar, etc.) to determine their location.  Modern travelers will use the sun + stars system.

If you travel beyond the solar system but within the local group of galaxies, the best way to navigate is probably using pulsars.  Pulsars are all unique - they rotate at varying speeds, and those speeds can be detected.  Finding 3 pulsars in the sky, and having a catalog of known pulsar speeds would allow you to ID the three pulsars and triangulate your position anywhere in the galaxy.

Essentially any time you can get 3 fixed points of reference in the sky, you can determine your exact position.