Design thinking is a human-centered approach to problem solving that relies on three main principles: empathy, collaboration, and experimentation. It involves understanding user needs through discovery, developing ideas through interpretation and ideation, and making ideas a reality through prototyping and experimentation. The process is non-linear and involves divergent and convergent thinking. Key tools used in design thinking include observation, interviews, storyboarding, paper prototyping, and other methods of understanding user needs and testing potential solutions.