Design thinking may have a lot of definitions, but it is a critical part of product development. The principal focus is understanding who we are creating products for, what their needs and problems are, and how we can solve for them. It puts the focus on the people behind the products, which is important, because we can often get lost in dollars, business value, feature prioritization, costs, technical specs, etc. While these are important, they don't make for splendid experiences.
What is Design Thinking - IDEO really popularized design thinking and human-centered design, so this is a post straight from them on the subject. An enjoyable read.
User Experience is Design Thinking - Another good article on the subject. "In essence, the Design Thinking process is iterative, flexible and focused on collaboration between designers and users, with an emphasis on bringing ideas to life based on how real users think, feel and behave."
The Business Value of Design (Podcast) - You can't be a business without design. It's a matter of how conscious we are about it. Design thinking is a problem-solving approach that is optimized for dealing with uncertainty, and for that reason is a critical tool in the tool belt.
What is Product Design (Podcast) - Eva and I explore product design deeper and discuss its importance to product development.