Docker is considered a PaaS (Platform as a Service) that uses OS-level virtualization to deliver software packages called containers. Compared to virtualization by partitions, Docker provides a very different and modularized way to host services on a machine. Creators of technologies and languages create Images that, when applied to containers, use microservices or microkernels to run applications. This removes the unused computing resources needed to run an application and heavily reduces the time spent setting up the application environments. Additionally, Docker provides a replication tool called Swarms, which makes it super easy to scale up an application in the form of distributed computing.