If you're using Opensuse (as for the gecko logo in your post) you can check exactly where files have been installed using:
rpm -ql package_name
and if you want to know just where the executables are placed, pipe the output of the above to grep bin
. Regarding sofwtare compiled/installed from source, you generally take control of the installation directories using the --prefix option in the configure step. Furthermore, running ./configure --help will tell you about other prefixes you can change at your pleasure. Anyway, I guess only the first part of my post answers your question, doesn't it?