Undrestanding docker: what is the dockerhub Ubuntu image?

  docker, linux, ubuntu

I configured Windows Subsystem for Linux, installed a Microsoft packaged Ubuntu on Win 10, to get my hands on Docker using Linux. From what I understood, Docker does not need a guest OS, unlike VMWare – that’s one of the main advantages.

I browsed the dockerhub and found an official Ubuntu image. What is it for, as there is no need of a guest OS?

Source: Docker Questions