The History API is an API that is mainly used to detect the user clicking the back and forward buttons while not leaving the page. It can also make you go to certain page in your browser history (don't worry, JavaScript can't actually see the history). The refresh part of the challenge was a bit misleading, as you cannot actually do this using the History API. It can also change the page URL displayed in the browser without actually going to the page displayed.
See the below links for learning about the History API:
To use the History API:
history.back();//goes back a page
history.forward();//goes forward a page
history.go(-1);//Goes to a page in the history, where negative is backwards and positive is forwards
history.pushState({name:"anything"},"title", "URL");//displays URL in browser without navigating there