A software package can usually be configured at compile-time to enable or disable certain options. When you install DebianPackages on your computer, you may need to know which options were enabled by the package maintainer.
Some programs have a command-line switch which will show which compile-time options are available. The man pages will usually document this switch if it is available, so this is the first place to check.
If this isn't available, check the Debian Changelog. Many maintainers add log entries if they change the compile-time options.
Failing this, you can download the source package using this command:
apt-get source <package-name>
Go into the directory which is created and look at the file named "rules" in the "debian" folder. This file contains the commands used to generate the package, and will include the commands used to configure the package for compilation. The most straightforward approach is to search for "configure" or "conf".
Figuring out the exact configuration options can be tricky in cases where multiple binary packages are built (with different options) from the same source package.