This is a clustering algorithm for the Google Maps API
Whenever the user clicks on a cluster, the zoom ratio is adapted and the locations in that cluster are show.
Other clusters will appear if the stage is not big enough to show them all with the new zoom ratio.
Practically it manages all markers on the map and summarizes them to "clustered markers" if there is not enough space around them.
A demo is included in the download package that will help users understand how it works.