dpkg (Debian Package) is package management system in Debian and other Linux distros based on it (Ubuntu, Mint).
Like so many things in Unix world, dpkg is more than one thing. Here are the meanings:
- dpkg a pakage management system
- dpkg is a tool (a Linux command)
- dpkg is a software management database (in /var/lib/dpkg)
- dpkg is a collection of tools serving the same purpose (dpkg-*)
dpkg is a low level tool, meaning it's great for basic package management things like maintaining list of packages (that package database mentioned above) or installing a speific package (but without checking dependencies or things like this).
dpkg deliberately doesn't get updated for more complex things as there is another family of tools doing that – called apt.