Unlike many other survival games, your Valheim character is playable across multiple worlds. In other words, when you start a new game from scratch, you get to keep your character with all his/her skills and inventory. (This may not seem quite right if you want to truly start again, but you can always just start a new character as well.)
So – it makes it even more important that you get your character right from the start, even if you’re thinking of restarting again before much longer.
There aren’t many options for your Viking. You can set the gender, hair colour and style, skin tone, and name. This is the first thing you do, before either creating a new world or joining a server with one already running.
As soon as you get into your new world you will start learning and improving your skills. Again, it is different to most other games of this genre – instead of building up points and spending them on improving stats of your choice, your actions in-game directly influence your abilities. Just like in real life, the more you do something, the better you get at it. This might be your physical athleticism (running, jumping, swimming), your skill at wood-cutting, or the damage you deal enemies (or friends) with your axe, spear, bow, etc.. There are a large number of skills, and they all level up differently depending on how you play the game. That makes your character much different than your friends after a just short time in the game.
You can quit and start a new character if you like – then you can go on to the same world, but with no skills or inventory, or you can go on a new world. Alternately, you can load up the same character, and go into a new world with that one. You will have the same skills, and you will even have the same items in your inventory as you had before. This will mean, for example, that if you already have an antler pickaxe, you won’t need to fight Eikthyr again to get back to the same technology level.