The document discusses diffusion theory as it relates to fashion trends. Diffusion theory proposes that new styles and innovations are adopted in a population over time through different groups - innovators, early adopters, early majority, late majority, and laggards. It describes how early adoption starts with higher social classes which then trickles down to lower classes. However, more recent theories argue trends spread more democratically through various groups and digital communication rather than top-down hierarchies. The theory helps understand how trends emerge but works better for behavior adoption than prevention and may oversimplify complex fashion innovations.