The Diffusion of Innovation theory, proposed by Everett Rogers, explains how, why, and at what rate new ideas and technology spread through cultures. According to the theory, there are five categories of adopters:

1. Innovators (2.5% of the population) are risk-takers willing to try new ideas.
2. Early Adopters (13.5%): They are opinion leaders who adopt new ideas early but with more caution than innovators.
3. Early Majority (34%): They adopt an innovation after a varying degree of time. This time of adoption is significantly longer than that of the innovators and early adopters.
4. Late Majority (34%): They are skeptical about innovations, only adopting them after the Majority of society has tried them.
5. Laggards (16%): They are the last to adopt an innovation. They generally rely on traditional methods.

Understanding this theory is vital for marketers as it helps strategize product launches and marketing campaigns. They can tailor their approach accordingly by identifying their target audience's category. For instance, if targeting early adopters, marketers might focus on showcasing innovative aspects of the product, whereas communication for the late Majority might emphasize reliability and wide acceptance.