For questions about the use, design, function etc. of APT (Advanced Packaging Tool), the standard software package management system for Debian and its derivatives.
Here's some basic functionality offered by APT:
install/remove a software package (requires admin privileges):
apt-get install/remove pkgname
display basic info about a package
apt-cache show pkgname
display packages whose names and/or descriptions match the search pattern
apt-cache search pattern
Here's a usage comparison with other package managers.
APT logs its activities in
The Debian Administrator’s Handbook includes two chapters which help understand APT: Packaging System: Tools and Fundamental Principles and Maintenance and Updates: The APT Tools.
Commonly asked Questions: