Explanation:

Econometrics is a practice which uses statistical techniques to help describe economic relationships.

Economists use econometrics to build models, which they can use for forecasting. To use an example outside of advertising, an economist might want to understand how average wages are affected by economic growth. They could use econometrics to help describe that relationship, showing how much average wages change when the economy grows. And they could then use that to forecast changes in wages, based on how they expect the economy to grow. These same techniques can be used in advertising. A marketer might, for example, want to show the relationship between how much they spend on TV advertising and growth in sales. Econometrics would help them do that.