As soon as we press the enter key after the command, the below sequence will be followed.
1. Check alias and then execute the command(shell-built-in or external command) accordingly
2. Shell built-in command
3. External command
Note 1: If command is executed with absolute path then external command or script will run. Else above sequence will be followed.
Note 2: If PATH value is empty, then shell will presume that the command is available in the current directory and hence it will try to run it from current directory.