When you install an application in Linux, the system usually put the executable binary  in the /usr/bin/ directory, but some applications might choose another directory to place the executable in.

So if you want to know where the executable of an application resides, you can use the which command:

which lightdm

The command mentioned above will output the location of the executable binary of lightdm which is:


Another Command:

In case you want to get more information about an application, you can use the whereis command which is designed to locate the binary/source and manual sections of a given application:

whereis gimp

The result of the aforementioned command will be:

gimp: /usr/bin/gimp /etc/gimp /usr/lib/gimp /usr/bin/X11/gimp /usr/share/gimp /usr/share/man/man1/gimp.1.gz