It's a "Resource Extraction Site", they're found in the rings around planets (usually gas giants). NPC miners go there to mine and NPC pirates try to rob them, and you can go and bounty hunt the pirates.
There's a Low RES (easiest), RES (medium difficulty), High RES, and Haz RES (the most difficult). Low/Med/High all have system security in the RES that are patrolling the area and can help you fight pirates. Haz RES has no system security and the Wanted ships are tougher.
If you're in a populated system and it has a ringed planet, it often has a RES in the rings. There won't be one far from you. You can see them on your left-hand targeting panel when you're within 1000ls of a RES. If you're docked at a station currently, it may not show up, but once ya leave the station if you're within 1000ls you'll see them.
What system are ya in? I can help you find a Low RES.