Preferential attachment is a concept in network theory that suggests that nodes in a network tend to attract new links based on their existing number of connections. In other words, nodes that are already highly connected are more likely to continue to attract new connections compared to those with fewer connections. This leads to the formation of "hubs" or highly connected nodes in a network. Preferential attachment is often used to explain the emergence of power-law distributions in networks, where a small number of nodes have a disproportionately large number of connections. This concept has been studied in various fields, including social networks, citation networks, and biological networks.