Breadth-First Search (BFS) is a graph traversal algorithm that explores all the vertices of a graph in breadth-first order, i.e., it visits all the vertices at the same level before moving on to the next level. It starts at a given source vertex and explores all the vertices that are reachable from it.The algorithm works by maintaining a queue of vertices to be visited. Initially, the source vertex is added to the queue. Then, while the queue is not empty, the algorithm dequeues the next vertex and visits all its neighbors. If a neighbor has not been visited before, it is added to the queue. This process continues until the queue is empty, meaning that all reachable vertices have been visited.BFS can be used to solve a variety of problems, such as finding the shortest path between two vertices, checking if a graph is bipartite, and finding the connected components of a graph.The time complexity of BFS is O(V+E), where V is the number of vertices and E is the number of edges in the graph. This is because each vertex and each edge is visited exactly once.Overall, BFS is a simple and efficient algorithm for exploring graphs in a systematic way.