Accounts receivables are debts owed to your company, usually from sales on credit. Accounts receivable is business asset, the sum of the money owed to you by customers who haven’t paid.
The standard procedure in business-to-business sales is that when goods or services are delivered the come with an invoice, which is to be paid later. Business customers expect to be invoiced and to pay later. The money involved goes onto the seller’s books as accounts receivable, and onto the buyer’s books as accounts payable.
Be sure to read up on accounts payable as well, and check out How to Read Your Business’s Balance Sheet and The Key Elements of the Financial Plan.