A* search algorithm
A* is one algorithm in a big group of similar algorithms. These algorithms are all different ways of finding a path between two places, over certain paths between them. They are called path-finding algorithms. "Places" and "paths" aren't always real places, though. They can be abstract, and they can be a metaphor for something else. One example where it is a real place is trying to find a road trip on Google Maps or Mapquest. In this example, the paths are roads, and the places are houses or cities. A second example is sending information over the Internet. The information needs to go through many computers to get to the end. Many routers use A* to find the best way to send information across the Internet. Here, the paths are cables, and the places are computers. For a third example, where it's not literal, you want to make a certain chemical from the ingredients you have. Mixing some of these ingredients will produce new chemicals, and those can be mixed with each other. A path-finding algorithm could tell you which order to mix them in. Here, the paths are chemical reactions, the cost is how long the reaction takes to finish, and the places are the different chemicals you can make.