Tracker is a bundle of apps that catalogue file contents to allow quick search of all sorts of text content, exif data from photos,tage in music and many other types of metadata. It can be very useful in making metadata easily available for certain apps and tasks. The downside is that it can slow your system down, especially if you have a hard disk as the boot unit since it is drive heavy when indexing. The indexing phase may take several hours depending on how much data you wish to index, beyond that the performance inpact is not noticaeable and the worst bugs seems to have been iron out many years ago. The remaining consideration is that the catalogue can become large, easily surprassing 10 gigabytes if you have several hundreg gigabytes of mixed files.