Difference between sellers account and business

assuming you mean Amazon Business, that is essentially the front end buying portal for businesses. You normally apply for this but it is setup for businesses to make purchases with PO numbers and pay on preferential 30 day credit terms.

Seller is as suggests the selling side of things. As you are on the forum I assume you have some sort of selling account. This will either be an Individal or Professional account (which you should be able to identify from within account Info from seller central homepage). An individual account is purely for selling off second hand goods, while the professional account is for new goods sold for profit (ie as a business). If professional amazon will require various elements of proof you are a business (it depends what kind of business you advise you are)