A subgraph is a portion of a larger graph that consists of a selection of its vertices and the edges connecting them. In graph theory, a graph is made up of nodes (or vertices) and lines (or edges) that connect these nodes. A subgraph retains the structure of the original graph but focuses on a specific subset of its elements. Subgraphs can be used to analyze specific relationships or patterns within a larger dataset. For example, in social networks like Facebook or Twitter, a subgraph might represent a group of friends or followers, allowing researchers to study interactions within that smaller community while ignoring the rest of the network.