Example
In this type of image addition, one image can be used several times without duplicating its URL, making it a good choice when using one image multiple times in a document.
Markdown Source
Picture of Duck:
![Duck][1]
Same picture of Duck:
![Same Duck][1]
[1]: http://i.stack.imgur.com/ukC2U.jpg
HTML Output
Picture of Duck:
Same picture of Duck:
