To find information (description) about installed packages on a Debian-based Linux system, such as Ubuntu, you can use the apt-cache command.
The apt-cache command is a tool that allows you to view information about packages that are available in the package repositories, as well as information about packages that are installed on the system.
To find information about an installed package, you can use the apt-cache show command followed by the name of the package. For example, to find information about the foo package, you can run the following command:
apt-cache show foo
This will display detailed information about the foo package, including the package description, dependencies, and installed files.
You can also use the apt-cache showpkg command to view information about the dependencies and reverse dependencies of a package. For example:
apt-cache showpkg foo
This will show a list of packages that depend on the foo package, as well as a list of packages that the foo package depends on.