Definition:

Revenue is the money earned through sales of products or services. It is recognised at the moment the product or service is provided to the customer, not necessarily when payment is made (see “Revenue Recognition” for more info)

Example:

If you sell 100 gadgets for $500 each, in the period you deliver them to the customer, your revenue will be $50,000.

Why it matters:

Revenue is shown at the top of the income statement. It is primarily what keeps a business running.