In most businesses, what drives the balance sheet are sales and expenses. In other words, they cause the assets and liabilities in a business. One of the more complicated accounting items are the accounts receivable. As a hypothetical situation, imagine a business that offers all its customers a 30-day credit period, which is fairly common in transactions between businesses, (not transactions between a business and individual consumers).
An accounts receivable asset shows how much money customers who bought products on credit still owe the business. It's a promise of case that the business will receive. Basically, accounts receivable is the amount of uncollected sales revenue at the end of the accounting period. Cash does not increase until the business actually collects this money from its business customers. However, the amount of money in accounts receivable is included in the total sales revenue for that same period. The business did make the sales, even if it hasn't acquired all the money from the sales yet. Sales revenue, then isn't equal to the amount of cash that the business accumulated.