Final answer:
The term to describe when marketers use digital media to gauge public opinion is 'crowdsourcing'. This process taps into a vast pool of individuals for their opinions or needs, especially through online platforms.
Step-by-step explanation:
The term used to describe when marketers use digital media to find out the opinions or needs of a crowd is crowdsourcing. This process involves obtaining needed services, ideas, or content by soliciting contributions from a large group of people, often through online platforms. Whether it's a marketing manager seeking information about customer demographics or a political party wanting to gauge voter reactions to a debate, crowdsourcing allows for a wide range of public opinion to be collected and analyzed. By utilizing modern digital platforms such as social media, public opinion surveys, and targeted questionnaires, marketers and researchers can rapidly gather data and insights from various demographic groups to inform their strategies and decisions.