- The branching factor is the number of children at each node.
- The effective branching factor is the number of children generated by a “typical” node for a given search problem.
A full-width search sees everything upto its horizon, and nothing beyond. This is called horizon effect. There’s a possibility that the moves looks great until the horizon and might turn bad afterwards.
A quiescent search is an additional search starting at the leaf nodes which tries to solve the above issue. In principle, any move which may destabilize the evaluation function is not quiescent.
Depth-limited search algorithms need a quiescent search to avoid errors.