Hi Anja – We offer several types of Facebook integration, including:
– A Facebook widget, which allows people to “like” a Facebook page.
– A Facebook share button, which allows people to easily share a post on their own Facebook timeline.
– A Facebook social icon, which links to a Facebook page. (Available via social links menu or social icons widget.)
More info here: https://en.support.wordpress.com/facebook-integration/
There isn’t an option to “like” an individual post on Facebook via the blog. If that’s a feature you’ve seen elsewhere, I’d love to take a look, so feel free to drop a link here.
Hope this clarifies things – just let me know if you have any other questions!