What files are installed on your system varies from package to package. To be 100% sure you should take a look into the
.deb package yourself. Download the package first.
First you need to extract the
ar vx mypackage.deb
Now this should result in three new files:
data.tar.gz. You're interested in the last one.
Now you can extract it as well using
tar xzvf data.tar.gz
Now you can browse the package content freely. Look for any makefiles, install scripts and such like to see where things gets installed.