I am here to show you two examples of using dpkg to query package info.
To know what deb package is installed, you can do this
Usually we do this with grep, to filter only info that we are interested in, let say i want to know the packages consist of keyword gcc.
dpkg -l | grep gcc
If I want to know the binary files are from which deb package, i can do that, let say i want to know for gnome-help.
dpkg -S `which gnome-help`
which is to shows the full path for gnome-help and it uses back quote to pass the result to dpkg.