Google Desktop is an application for Windows, MacOS and Linux that allows users to search the files located on their PC in much the same way as internet searches are performed. Traditionally, searching for local files has been done by file name only. More in depth searches, like searching for a particular word within a file, are slow due to the fact that each file has to be opened and searched individually. Google Desktop avoids this issue by indexing files, which means the contents of local files can be quickly searched.
Google Desktop also provides the ability to run desktop widgets (known as Gadgets), which can be freely downloaded and used across all three operating systems.