This is an open world medium-low difficulty survival game. The backstory can be given in about one line: "odin put you here to kill some bad guys (bosses)". The game is about evenly split between combat, exploration, resource gathering, and building -- of course eventually exploration is no longer useful nor profitable beyond for fun, and you don't have to keep building if you don't want to after you have a functioning base, but most players enjoy building bases as a big part of the experience.
Its closest to no mans sky, to me ... wander around doing what you feel like doing each day, with a home and such when you want it.

the developers have done an OUTSTANDING job of making the game fun, mostly bug free, and high quality for the parts that are already done. Its not a EA to get a tiny sample of the content and then wait for years. Have no fear playing it early, it should not crash or give you beta testing blues; they dont wipe you out every month and make you do it all over, etc. The only thing about it being EA is more stuff will keep coming in and occasional rebalance of things (also rare, think there have been 5 total of these and only 2 were major).