I like the UK’s Chartered Institute of Marketing definition of Marketing for its simplicity and focus on the customer. It highlights the need for research to identify customer needs and interests and to check that they are satisfied.
The CIM define marketing as:
“The management process responsible for identifying, anticipating and satisfying customer requirements profitably”
Naturally, it talks about the commercial focus also, less relevant for not-for-profit marketing.
It follows, that for my focus, integrated digital marketing strategy, the goal of digital marketing should be to support this