Ubuntu (Linux) follows the filesystem hierachy structure. There is a description of the main directories in that link.
The location where software gets installed depends on how you install it. If you use the most obvious method (Ubuntu Software Center/
.deb's) it generally gets installed to the default locations. In that case libraries will end up in
/usr/lib/ (Libraries for the binaries in
/usr/sbin/.) and the executable in
/bin (Essential command binaries that need to be available in single user mode; for all users, e.g.,
/usr/sbin (Non-essential command binaries (not needed in single user mode); for all users).
Some other important directories are
/opt: Optional application software packages. Jasperserver (a stand-alone and embeddable reporting server) for instance installs into
/usr/local is for data that must be stored on the local host and is used for installing software/data that are not part of the standard operating system distribution. In this directory you will find
lib for libraries en
bin for executables.
You can use
main menu to browse for executables. Or from command line with
locate. Or inside
Ubuntu Software Center you can browse all the files that are used for a package. Examples using
locate libreoffice|grep bin
Sidenote: Eclipse is in the software center so no need to download a zip (unless you want the newest version and not the most stable one):