Email Campaign is a planned email send or series built around a specific message, audience, and objective.
It matters because email is one of the few channels a business can own directly. Strong email fundamentals improve trust, deliverability, segmentation, and long-term lead nurturing.
Example
A training company announces a new workshop to opted-in contacts interested in that subject. The campaign has a defined audience, registration destination, send schedule, and way to measure completed registrations.