Social Share Buttons

Hello all,

Is there an inside theme feature that allows you to add social buttons to posts?
I need Facebook and Twitter added to the excerpts of the posts in the blogroll as well.

I saw a feature on someone’s website where when you share a post to Facebook, the meta description (the excerpt) becomes an image where the thing is written on an image background and gets shared with a link to the respective page. I imagine this happens by preliminary setting a background image to be used for every text and then the text is simply visually plotted on that background.

I wonder if you guys know something about this.