The Mail Body is simply the content of the message, in whatever format it was created in.
One little tip if you are creating a message in a simple Email Client and want to put a signature at the end, simply start a new line with two dash characters followed by a space and then a newline. Then put the contents of your signature. Any suitably capable Email Client that sees the dash-dash-space sequence will be able to show this differently to allow easy differentiation between the main body of the message and the signature.
Mail Body
The Mail Body is simply the content of the message, in whatever format it was created in.
One little tip if you are creating a message in a simple Email Client and want to put a signature at the end, simply start a new line with two dash characters followed by a space and then a newline. Then put the contents of your signature. Any suitably capable Email Client that sees the dash-dash-space sequence will be able to show this differently to allow easy differentiation between the main body of the message and the signature.