All characters on the core get logged out & are rerolled
All unsold items on the market expire.
You keep your profs & items.
Any guild points you earned will stay by your name until you leave that guild. Any guild points earned will stay in that guild forever.
You lose extra stats from your pass/fail ratio because you have no fails for the season.
You lose extra stats from objectives, pots, gylphs because your character was rerolled.