Breadth-first search (BFS) is an algorithm designed for traversing tree or graph data structures, starting from a root node and exploring all neighboring nodes before moving deeper into the structure. The document details the BFS method, including steps for exploring nodes and provides examples of applications, such as solving games and algorithms like Dijkstra’s for finding shortest paths. BFS effectively guarantees that nodes are explored in order of their distance from the root, making it useful in various computational problems.