BFS stands for Breadth-First Search, which is an algorithm used to search a tree or graph data structure for a node that meets a set of criteria. It starts at the root of the tree or graph and explores all nodes at the present depth before moving on to the nodes at the next depth level. BFS uses a queue data structure for traversal, and it traverses the graph in a breadthwise direction. The key steps of the BFS algorithm are:

• Pick a node and enqueue all its adjacent nodes into a queue.
• Dequeue a node from the queue, mark it as visited, and enqueue all its adjacent nodes into a queue.
• Repeat step 2 until the queue is empty.

BFS is useful for finding the shortest path between two nodes in a graph, determining the level of each node in a tree, and evaluating nodes in a graph. The time complexity of BFS is O(V + E), where V is the number of nodes and E is the number of edges.