Centrality is one of the core principles of network analysis. It measures how “central” a node is in the network. This is used as an estimate of its importance in the network.
However, depending on the application and point of view, what counts as “central” may vary depending on the context. Correspondingly, there are a number of ways to measure centrality of a node.
degree centrality, closeness centrality, betweenness centrality, and eigenvector centrality