Open Graph
Open Graph is a technology first introduced by Facebook in 2010that allows integration between Facebook and its user data and a website. By integrating Open Graph meta tags into your page’s content, you can identify which elements of your page you want to show when someone share’s your page.
For example, you could use the og:image tag to specify what image you want Facebook to use when your page is shared. By specifying Open Graph information, Facebook doesn’t have to guess what information to use when your page is shared.