Social media apps like Facebook, twitter linked allow your website and apps to share on there pages to reach with more peoples.

Question is how to check your post will be look liked on Facebook and other social media website, answer is here, below some links helps you to give virtual look how your page look if share 

Facebook

https://developers.facebook.com/tools/debug/sharing/

Twitter

https://cards-dev.twitter.com/validator

LinkedIn

https://www.linkedin.com/post-inspector/

Note- you need to login to use some of them and links are working till date of this article post