Diffusion Theory explains how new ideas, technologies, or practices spread within a society or from one society to another. It emphasizes the process by which innovations are communicated through various channels over time, influencing individuals and groups. Key factors include the characteristics of the innovation, the communication channels used, and the social system in which the diffusion occurs. The theory categorizes adopters into groups: innovators, early adopters, early majority, late majority, and laggards. Each group has different motivations and readiness to embrace change. Understanding these categories helps in predicting how quickly an innovation will be adopted within a population, impacting areas like public health, marketing, and education.