Classes slightly change game play on Res.
Members of the Rancher Class have three hatches a day and can open a rancher shop to sell pets
Members of the Merchant Class have one hatch a day but get a discount in NPC shops and can open a Merchant shop.
You can change your class for free by going:
Prefrences under your log out button)> Class change
You only get four free class changes but the tokens sold in the CS will let you change your class if you've ran out of free changes.