How is called this thumbnail slider feature

I am new to wordpress, and I am trying to create new website. I found really nice-looking theme, but when I installed and activated it, it looks very simple compared to the preview page. Is it due to that I have to pay to make my website look 100% similar as preview?

Anyway, how is this feature called, that you can see in the picture? There are 3 thumbnails, that are sliding after some time, and they are clickable. Could anyone share the name, and how can I implement it myself?

Many thanks!