There are three modes. You can switch between them at will, but must log out of the game to do so. Logging out during combat is frowned upon, and considered an exploit by the developers.
- Solo. This works pretty much just like the original game. You'll see NPCs, but not any humans.
- Closed group. You need to apply to join these and be added (unless you have other players and want to start one yourself). These groups can permit PvP or forbid it depending on their ruleset. The biggest private group is Mobius. You will see other CMDRs, although fewer than in the next mode, which is
- Open. You are in the open group and wil be instanced with other CMDRs. Some may want to kill you, others may not. Where you are has a great influence on that dynamic. Around Lave, for example, you'll see a lot of players, including gankers and pirates. Exercise extreme caution when there and thereabouts.
I played solo for about 20 hours to get the basic controls automatised, memorise my control scheme and get my head around the basics of the game. I've played hundreds of hours of Open since then. The only times I've been killed by CMDRs were accidental - once when a CMDR and I rammed each other in a combat zone (we both died), and once when my alliance colleague blew me up accidentally when we were practising combat. I have no interest in the Lave cluster, and moved away from the starter systems pretty sharpish, so don't often see CMDRs I don't know.
I've killed myself far more times flying like a dumbass after a few drinks than I have been murdered. I totalled my A-graded Asp just last night when I forgot to throttle back while flipping in flight-assist off mode to line myself up for the entrance to a station. I ended up flying it at full throttle into the superstructure.