When you enter in a link on a Facebook post, Facebook scrapes that page for images, page title, page description, page type, etc.  You can check out how Facebook will display your webpage on a post, and what data it gathers from your webpage by entering in your webpage url in the Facebook tool at:

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UltimateWB Full software comes with a Facebook meta generator app that you can turn on and configure which Facebook meta tags to include in your pages.  You can read more about the Social Meta Tags app on the User Manual article at: How to automatically add Facebook meta tags to your webpages

Facebook Sharing Debugger:

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Use this link to check for any errors or issues on what Facebook scrapes from a webpage for Facebook sharing.