Search Line
The Search line filters the package tree so that only those packages whose name or summary contains the search string are displayed.
Find Package
The Find Package dialog searches the names of the packages in the package tree and moves to the next matching package. If Sub string is not set then it will find only exact matches against packages names. If Wrap search is not set the search doesn't wrap around the end of the package tree.
Find File
The Find File dialog searches for files the names of which contain the search string. The columns in the display are:
Installed - Ticked if it is an installed package.
Type - The type of the package.
Package - The name of the package
File Name - The name of the matched file
Only the files in installed packages are shown unless Also search uninstalled packages is set, this will only work with Debian APT packages and only if the apt-file command installed. The database used by the apt-file command is updated by the menu item.