To anyone who finds EVE fascinating, but doesn’t actually want to play it themselves, I can highly recommend the “Empires of EVE” books by Andrew Groen. The two volumes span the time from beta to 2014 and talk about the wars and empires of Null Sec. The author interviewed loads of players. It’s a fascinating read.
In EVE everything within 1000km is on the same “grid”. within a solar system you can only warp to known locations. That includes locations that were manually saved or celestial objects like moons and planets.
That means when someone warps to a moon, they can see anyone who warped to that moon, since they are on the same grid.
A safe spot is a location that isn’t on the same grid as a known location. You can still be scanned down by someone, but there are ways to know about it.
Edit: Its been a while and I’m no expert, so anyone feel free to correct me.