Graph algorithms are a subset of algorithms that operate on graphs, which are mathematical structures representing relationships between pairs of objects. Graph algorithms are used to solve a variety of problems and are essential in various fields such as computer science, operations research, and social network analysis. Some common types of graph algorithms include shortest path algorithms (e.g. Dijkstra's algorithm), minimum spanning tree algorithms (e.g. Prim's and Kruskal's algorithms), and graph traversal algorithms (e.g. depth-first search and breadth-first search). These algorithms are used to find the most efficient routes, analyze connectivity patterns, and identify important nodes in a network. Overall, graph algorithms play a crucial role in solving complex problems related to networks, transportation, social interactions, and other domains where relationships between entities need to be analyzed and optimized.