Enter a directory and a file pattern. The directory field has a help list which is set with the various directories entered in the preference dialog.
Enter a list of words separated with spaces. A checkbox lets you control the selectivity of the search (only packages matching all keywords).
A package contains several sections. You can search in the section you want. Here is a small description of each:
This is a one-line description of the package.
This is a longer piece of text describing the package.
This is the list of all files (directories and files) in the package. The various file paths are compared with the keywords.
This is a list of package dependencies (what is needed by the package to install and operate normally). This might be used as a quick way to find out which packages need a given library, for example.
This lists the service delivered by the package. This list corresponds to libraries and utilities.