Imagine you are passing grades in elementary school. You send the following message:
From my part To: Jeff Message: I want to fight with you for the flagpole after school
You pass this message to the person next to you and they transmit it … and the message finally reaches Jeff. Jeff is now very confused, because he's pretty sure he just sent a message about fighting with the flagpole after school … but he does not remember sending it … and if he tries to answer, he'll get even more confused and , finally, just drop the note on the ground and forget that it ever happens.
To a computer
127.0.0.1 Is essential
I Specifically used for a computer that talks to itself (for example, communication between processes)