One of the most important things that businesses need is to make a profit, in order to make that profit, there are many different things that must be considered. Most of these companies will sell their products in hopes that they will make that profit. Their accountant will create the asset account "accounts recievables" to record the amount that a company stands to make should all the clients with balances were to pay them the amount owed. However in most cases the company does not recieve all of that money even at the end of thier fiscal year.
That being said the assets show the sales revenue when sales are made, and liablilities when expenses are incurred as well. Therefore the way it works is when ever a business takes money in for goods and services they increase the number of assets that they have. When they pay bills to run the business those are the liabilities.