E-mail messages are similar to letters, with two main parts:
The header contains the name and address of the recipient, the name and address of anyone who is being copied, and the subject of the message. Some e-mail programs also display your name and address and the date of the message.

The body contains the message itself.

Just like when sending a letter, you need the correct address. If you use the wrong address or mistype it, your message will bounce back to you--the old Return to Sender, Address Unknown routine.

When you receive an e-mail, the header tells you where it came from, how it was sent, and when. It's like an electronic postmark.

Unlike a letter, which is sealed in an envelope, e-mail is not as private. It's more like a post card. Messages can be intercepted and read by people who really shouldn't be looking at it. Avoid including any confidential information unless you have a way to encrypt it.