Email is the acronym for Electronic Mail and you can consider it to be on the same lines as Post Cards/letters being sent via Post Office/Courier Service. It is the most convenient way to communicate in this era of Computers. Nowin case of letters you need to specify an address similarly, to send an email you need the email address if the person to whom you want to send an email. Wherin it takes a few days for the letter to reach after you send, the email reaches in a fraction of second to the recipent after you send it.