It's not dissimilar from mechanics in other games, implicit in my comment is that none of the 3 EV games had any sort of stealth mechanic. (ETA: Actually, they had cloaking devices, but they were special unique items that you couldn't transfer if you upgraded your ship. Not sure if that exists in Naev, I haven't gotten very far into the main story.)

You can go into stealth, and other ships have a bubble around you can see on your radar (the radar is also much better than in EV). If you get inside that bubble you'll fall out of stealth. The size of the bubbles scales with the mass of your ship, so a shuttle or an interceptor can hide very effectively, but massive cargo ships simply cannot.

This makes being a criminal or smuggler much more interesting. In EV there was nothing more to it than being super fast and staying ahead of the patrols trying to scan you. In Naev it's the similar, but stealth gives you more options. It feels very cool to be drifting silently in space, waiting for patrols to move away so you can reach the jump point undetected. Feels more deliberate and clever.

Another cool thing is that the AIs use it too. So it feels much more like you've been accosted by a highwayman when you're a little Terrapin trying to finish a mission, and suddenly pirates appear out of the blue (black?).