It doesn’t matter whether you’re using Windows, Mac OS, or a Linux distro like Ubuntu, the names programs display in the titlebar and the names of the actual files that run them can be quite different. A familiar example for many would be Microsoft Office Word (or Word for Windows in the old days) – or winword.exe, to be precise.
In Ubuntu, you can guess the package names of many programs simply by making all characters lower-case, and perhaps removing a space between words, or even abbreviating it. For example, KAlarm is actually kalarm, tovid GUI is tovidgui, and Downloader for X is d4x.
But you can’t guess them all, so you’ll need to look at the properties of launchers to the programs you want to know more about. Since you can’t really right-click launchers in the Applications menu for this purpose, by far the easiest method is to temporarily add them to your panel (or desktop), then just delete them when no longer needed. You can actually get the properties of launchers while editing the Applications menu, but this method is simpler and quicker.
For any program you need to know the package name of, right-click it in the Applications menu and choose either Add this launcher to panel or Add this launcher to desktop. When you right-click the new launcher on your panel or desktop, choose Properties, and the Command field will reveal the program’s actual name.
Just remember to ignore any options on the end of a command, since a program name must be one word without spaces (this can of course include many words strung together with hyphens or underscores). So while Amarok‘s launcher says amarok %U, the %U is an option, and amarok is the command. Even if you can see nothing familiar, you can bet whatever the command starts with, and is before the first space, is the command. For example, Downloader for X is actually no longer d4x, and since the command string is now nt -a %U, one has to assume nt is now the name of the command that runs this program.
The exceptions to this rule are when the path or address of the command is specified, or when another command precedes it. A good example is gksu /usr/sbin/firestarter for Firestarter, as not only is the path specified before the command, firestarter, but in order to run it with superuser privileges, the whole lot starts with gksu (basically, sudo for GUI programs). In a situation like this, one would look to the end, not the beginning.
If you need to find out the version numbers of installed packages, read this.