Email can be as quick and convenient as a phone call. The recipient does not have to be connected for you to send them a message. They can connect at a later time and read and respond to your message when it suits them. When you post a message or letter to somebody via conventional mail, the letter is passed from one post office to another until it arrives at a post office close to its eventual destination. It is then delivered to that person's mail box.
Email works in a very similar way.
The post office is taken over by computer software programs and the delivery vans are the computer networks. It has a password to prevent others reading your mail. In order to read or send electronic mail you will need special software. There are many different email software packages eg. Outlook, Outlook Express, Netscape Mail and or Eudora.