It builds upon Spotlight, which comes preinstalled with OS X. It makes Spotlight both more powerful and easier to use.
HoudahSpot provides a clear and structured interface that focuses on file search. It gets you to your files as quickly as possible.
* Find files by name, text, content kind, author, recipient, pixel count, etc.
* Combine criteria to narrow down search results
* Specify which folders to search and which ones to exclude
* Add any of the hundreds of columns available
* Apply filters to reduce search results to only the relevant items
* Preview files and text matches
* Open files and, where the application supports it, continue searching for text matches by pressing command-G (Find Next)
HoudahSpot is indispensable to unearth hard-to-find files. It also works great as a replacement to the default Spotlight interface.
If you've ever had a hard time finding a file before, this is what you've been looking for.