Here is the video version, if you prefer it:
The which command shows you the location of a given executable. (Shotts, 2019) For example:
mislav@mislavovo-racunalo:~/Linux_folder$ which cp
/usr/bin/cp
It only works for executables, not for other command types.
Hope you learned something useful!
References
Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Pages 67-68