The whole map gets wiped, but you can lay down your base with 2 clicks as it was in the previous season. All items you got from the previous season carry over into the new one. Season content is only cosmetics, be it clothing, weapon skins, housing items and some healing stims, but nothing that allows you to get through content quicker or be more powerful than any other person in the game.
If I'm being honest, this game is pretty damn good not only as a F2P game, but just a survival game in general. It's fleshed out well, systems work good, building and crafting is nice, mobs are very diverse, events are great. Id recommend it to try for sure.