Two different ways of defining marketing; 1. “Meeting customers needs profitably” describes the art/science of identifying customer needs and delivering value to them profitably; 2. All activities done in order to promote and attract consumers to a product or service.
Marketing Management (Kotler and Keller): Textbook on Marketing 101, covers everything
Playing to Win (Lafley and Martin): More strategy than Marketing but in important read
Marketing Myopia: HBR
The 30 Things Customers Really Value
Seth Godin’s Blog
Boundless. Digital content for teachers; has some good Marketing 101 content