What is meta property="og:image" content?

Few hours before i edited one article is wikihow by replacing already existing image by my own image, after submitting that article i checked the page source of that article and my image is displaying in this format "<meta property="og:image" content="http://www.wikihow.com/images/a/ae/Black-shoes-mensusa.jpg"/>". i don't know what is the meaning of meta property="og:image" content? but my image is not displaying in the front end of the article. Please tell your answers..

 

This Meta tags tells wikihow, what images, texts, and more to use when sharing your webpage.
and the image meta tags directs wikihow to use the specified image when the page is shared.

 

og: are the meta tags which refer to "Open Graph" defined by Facebook. These meta tags are used by modern websites to define their presence on facebook. Open graph tags help to pull your defined picture when a user or you are trying to share a link on facebook timeline.

Open graph helps the webmaster to define the information which should be seen by the users on the facebook while they are viewing your image or other information on the timeline. Search for the facebook open graph meta tags on google.