You can find out where the files belonging to a package are if you know the package name. Open a terminal and do this:
dpkg --listfiles packagename
You will find that the files are split up by type and installed in various locations according to the file type. For example, binaries usually go in /usr/bin, library files in /usr/lib, manual pages will go in /usr/share/man and so on. In these directories you will find the files for many packages.
The reasoning for this layout can be found in a document called the Linux Filesystem Hierarchy Standard
. This is pretty dry reading, but there is some good info in there if you are curious about what should go where, and why.