If you have a photo on your computer, from a digital camera or something that has been scanned to produce a JPG, GIF, or PNG file.
Here are two choices for doing that:
Send the photo as an attachment to an email. It'll show up as an icon at the top of the email for the receiver to click and open in their picture viewer. This is the most common option.
Embed the photo into a HTML formatted message so it appears in the text of the message just like a photo in a newspaper article. This looks nicer for people who want to read the message and not necessarily work with the photo file. But there are compatibility issues to keep in mind.
Whichever way you choose, you need to keep an eye on the overall size of the message. With higher resolution cameras available it's easy to go over the recipient's limit for incoming messages.
There is a little more to it. Here is a link to a great newsletter that comes in handy again and again: Office-Watch.com