apt-getprogram uses this database to find out how to install packages requested by the user and to find out which additional packages are needed in order for a selected package to work properly.
While apt-file is a program to find missing package.
A sample to install and use apt-file
1. Install apt-file with apt-get -- sudo apt-get install apt-file
2. Update the apt-file database -- sudo apt-file update
3. Search missing package with apt-file -- apt-file search