A Docker container provides a way to run multiple isolated systems on a single server or host. Each container shares kernel (& libraries also) of the host???s operating system. And since each container that is being used, shares OS with host, it makes docker containers very light in size. In-fact size of a Docker container can be in Megabytes (not GBs) & they load up extremely faster in mere seconds as compared to virtual machines that are GBs in size & take minutes not seconds to load up.