Net margin compresses the whole income statement into one figure. Gross margin shows pricing power over direct costs, operating margin adds the cost of running the company, and net margin adds interest and tax to reach what shareholders keep.
Levels are only comparable inside an industry. Grocery retail runs on margins of two or three per cent and software on thirty or more, and neither number says anything about which is the better business on its own.
The direction usually matters more than the level. Margins expanding while revenue grows is the strongest combination in fundamental analysis; margins contracting as revenue grows says the growth is being bought with discounts or with spending.