The accounting needs of a business are quite different from that of a person. Businesses have customers that owe money, vendors which are owed money, employee payroll, more complex tax laws, etc. GnuCash offers business oriented features to facilitate these needs.

Accounts Receivable (A/R) are used by businesses to record sales for which they are not immediately paid. This is represented on the balance sheet as an asset, because the expectation is that you will receive payment soon.

Accounts Payable (A/P) record bills that businesses have received, but may not pay until later. This is represented on the balance sheet as a liability because you will have to pay for them.

A/R and A/P accounts are used primarily when you have a lot of bills and receipts flowing in and out, and do not want to lose track of them just because you do not pay or get paid right away. For most home users, A/R and A/P are too complicated to be worthwhile.