Command Types

What happens when I execute a command?

ls

There are some commands that are just executable files inside the disk that the system calls.

But there are some commands that are inside the command interpreter do not need any file to be executed.
This commans are executed in memory.

How can I know which type of command am I executing?
Using type

type cd

type is an internal command of bash

this means that cd is a command that runs in memory and is not located on a separate file.

type ls

ls is an alias of 'ls --color=auto'

here, ls is actualy an alias; this means that when the ls is called, ls --color=auto is executed instead like a macro.

but where is this command actually stored in disk? It's location can be found using:

whereis ls

ls: /usr/bin/ls /usr/share/man/man1/ls.1.gz

where we can see that the ls command is stored in the binary folder /usr/bin/ls

If we try the same command with an internal command like cd

whereis cd

cd: