In the spirit of better investing and in celebration of the first Worldwide Invest Better Day coming up on Sept. 25, Motley Fool analysts will be answering user- and reader-submitted questions leading up to the big event. "Ask a Fool" anything, and we'll do our best to help you invest better.

In the following video, analyst Austin Smith explains net margin, which is a company's net income divided by revenue or sales. It's important to note that net margins vary wildly by industry. For example, grocery stores have notoriously slim net margins, while software companies' are very high -- compare Safeway's (UNKNOWN:SWY.DL)

Click the big green button to join the thousands of people celebrating Worldwide Invest Better Day on Sept. 25!