A series of advertising messages that share a theme, and market a product or service. In the context of digital marketing, campaigns can be run through search and display network advertising platforms (i.e. Google, Bing), social media, email, or other online platforms. Campaigns can also refer to a comprehensive digital marketing strategy or project. It's a collection of ad groups or ad sets centered around a common goal.
Campaigns are also specific marketing activities to drive engagement, conversions, traffic or revenue, that tie in with the company/brand/organisation’s overall goals.