Some maps have unique objectives. On this asteroid for example you can mine for rare crystals which rewards points. Other maps have hidden treasures or equipment that needs repair. The points are used for buying gear, buffs or special attacks but also for winning the game, so don't spend it all.
There is always one quest active, complete it and get a new one. The missions can vary from walking to a checkpoint, killing certain monsters to helping other players - putting you in a dangerous spot. For example: Go over and give a player a bandage. Will he shoot you? Is it worth it? Other missions can require teamwork like summoning bosses and defeating them.
When the game starts you have nothing so you need to quickly gather points by doing various tasks. You can start opening chests once you have enough points to use as currency. Opening a chest gives you three choices, a weapon might be too expensive at the start so you could pick a buff or a special attack instead. A special attack would be a force-shield or a missile-strike for example which is a onetime use powerful effect.
You need weapons to fight off the monsters of the planet and there will be a wide variety of weapons. You may need to conserve your ammunition cause the drops are random and you never know when the next rare drop is coming.