The notation "K_n" represents a complete graph in graph theory, where "n" indicates the number of vertices. In a complete graph, every pair of distinct vertices is connected by a unique edge. This means that if there are "n" vertices, there will be a total of \fracn(n-1)2 edges, as each vertex connects to every other vertex. Complete graphs are important in various fields, including computer science, network theory, and combinatorics. They serve as fundamental structures for studying connectivity and relationships within networks. The simplest complete graph, K_1, consists of a single vertex with no edges, while K_3 forms a triangle with three vertices.