There are many different ways you can set up filtering of markers on a Google Map based on the markers' attributes. This page demonstrates four possibilities: a form, a drop-down menu, radio buttons, and plain text links.
All examples use the GV_Filter_Markers_With_Text() function, whose two named parameters are "field" and "pattern".
If you don't specify a field, both the name and the description are searched. So a very simple use of this function would look like this:
If you know how to create "regular expression" patterns, you can use them.
For example, the following function would select only markers whose name began with the letters A through F:
There's also a "zoom" option available, which will cause the map to pan and zoom to fit the area described by the markers that are visible: