回复：再问一下，那A/P,A/R 和bookkeeper, Accountant又有什么

In general, A/P is responsible for entering invoices information (i.e. the company buys anything), A/R is responsible for entering cash receipts and matching with the sales invoices (i.e. the company sells something and receives money for the service), Bookkeeping would be journal entry functions (by the way, this term is not used in big company).
In big companies, A/P, A/R and G/L functions are all separate and they are all called accountant. In small companies, one or two persons may do all of these.