An accountant is a person whose job involves keeping financial records for a business. To be a great accountant, you've got to be good at math.
When a company hires an accountant, it turns over the management of its accounts to that person, who is responsible for keeping track of spending, income, and any other financial information. An accountant is also held accountable for the accuracy of a company's books, and usually has to be officially certified before working in the field. The word comes from account, by way of the Old French aconter, "to count."