You can switch between modes (although, if you are in danger, you have to wait 15 seconds to log out (regardless of WHAT the danger is!)). There are three modes; Solo (where you will be the only Player in 'your' Galaxy, Private Group (invitation only, although you can have your own group and invite friends to join), and Open (where you could meet any Player who is currently playing the Game in 'Open' and is in 'your' area of the Galaxy.
Anyway, here is something that may be useful to know how to do; Fuel Scooping (for beginners). I am NOT going to explain FSD Boosts (because I haven't done it myself!).
First, of all the Star Types out there you can only scoop fuel from seven, and one of the mnemonics to remember these is KGB FOAM (so Star Types that are any of those letters can provide you with fuel, any other star will just provide you with hassle!). Second, you will need a fuel scoop! (there are few things more embarrassing than heading off on a long voyage only to find that, when you try to scoop fuel, nothing happens, looking in the 'modules' list shows you HAVEN'T fitted one, and now you have to call for help from "The Fuel Rats" (look 'em up!)). Now the complicated bit.
Once you arrive at a suitable scooping star aim outside the edge of the star and accelerate slowly forwards (no point in saying how far out to aim, as I don't know what size monitor you have). After a few seconds a gold ring will appear around the star) this is the 'Impact' ring and flying inside this ring will cause you to crash out of Super Cruise, taking damage, and making it difficult to head away from the star). Aim the same distance from the outside of the ring as the edge of the star is from the inside of the ring, and continue slowly accelerating. After a few more seconds the fuel scoop will automatically kick in. A display will appear in front of you, showing fuel flow, quantity (in the main tank), and temperature. Now stop and wait, but monitor the temperature of your ship; if it goes over 70% pull away, let her cool down, and try again (in my experience, when a ship goes over 70% while scooping the temperature can then climb rapidly).
Once your tank is full pull away from the Star and wait until the temperature drops below 50% before jumping to the next star system. This will allow your ship to warm up safely as the FSD spools up without the ambient temperature near the star causing your ship to exceed 100% and take damage.
As you gain experience in fuel scooping you can cut things finer, but these instructions should allow you to learn how to scoop safely.