Side bar – recent/popular with images

In your demo http://demo.alxmedia.se/hueman/ on the left of the page you have two options within that side bar; “Recent and Popular” and you can switch between them. Is this a custom widget? or is this built into the theme and I am missing how to activate it?

I’d love to have small thumbnails appear along side my recent posts on the left.

Thank you so much for your time and support with this theme!

Brandon