Facebook Requests are an easy way to let your user's invite their friends to any page of your site. They also allow you, the site owner, to send updates to any, or all, of your users about new blog posts, events, sales, or whatever you want. The requests are sent through Facebook and appear as either friend notifications or application notifications, depending on how they were sent from your site. Below is a description of each, and how to set both up.
As of April, 2015, Facebook requires that your site use the Facebook Canvas, which shows your site within Facebook.com. To use the Canvas, your site must have a valid SSL certificate for the root domain. The requests feature will not work without an SSL certificate and the Canvas area properly configured.
For more information on setting up SSL on your site, see our Obtaining SSL Certificates for Facebook guide.
Additionally, Facebook requests only work if you application is in the Games category. You can set the category in the "App Details" section of your application on developers.facebook.com.