No and no.
Valheim is a single player or co-op open world survival but loosely story led, meaning you have a purpose to fulfil. So only you or the other friends you have chosen to play together with will see your base (or bases).
It draws on elements from many games in the past, but with a new Viking fantasy twist and original artistic theme. It isn't hard to play, it can be beautiful to look at and you're free to build ramshackle hovels or mighty stone fortresses.
I bought it blind at release when I saw it was being published by Coffee Stain and so I didn't even know about 'the hype' the game gained. I have enjoyed 360+ hours of play and no regrets. I've temporarily shelved it for now until the Mistlands biome is released at the end of the year or more likely by Q2 of next year.
I hope that helps ;)