What it is
Net margin shows what percent of each dollar of revenue survives all costs plus interest and taxes.
Why it can be tricky
Net margin reflects a lot of things outside the business's day-to-day operations: how much debt the company carries (interest), where it's incorporated (taxes), one-time gains or losses. Two companies with identical operations can have very different net margins.
For pure operational comparisons, operating margin is often the better lens. Net margin is the right number when you care about what eventually flows to shareholders.