Command Behavior Types

The command type can tell us if a command is an external or internal one.
The command which can tell us the absolute route of a program.
The command uname -a shows information about the OS.

The shell supports two types of commands:

Internal: These commands are part of the shell itself are not separate programs. Their main purpose is executing tasks inside the shell.

Command	Description
cd	Changes the current directory
echo	Displays a line of text of variable value.
exit	Exist the current shell session.
pwd	Prints the current working directory.
alias	Creates an alias for a command.

External: These commands reside in individual files. These files are usually binary programs or scripts. When a command which is not a shell built-in is run, the shell uses the PATH variable to search for an executable file with the same name as the command.

Command	Description
ls	Lists the contents of a directory.
grep	Searches for patterns in files.
find	Searches for files in a directory hierarchy.
cp	Copies files and directories.
mv	Moves or renames files and directories.