Final answer:
A tag, as described to a new advertiser by a digital marketing consultant, is a piece of code used in web development.
Step-by-step explanation:
A tag, as described to a new advertiser by a digital marketing consultant, is a piece of code used in web development. In the context of digital marketing, tags are used to collect data and track user behavior on websites to optimize advertising campaigns. They are often inserted into a webpage's HTML code and can be used to measure conversions, retarget visitors, or enable analytics.