Docker is an open-source platform for making, deploying, and managing software in containers, which are small virtualised environments. It is mostly used as a software development platform for making apps that run on different servers and do not run on the same operating system as the servers they are on. Software that is packaged into containers does not have to be compatible with each other. It can be easier to build, deploy, maintain, and use software that is packaged into containers. Docker is similar to virtual machines in that it uses virtualisation to make containers for apps to store. Containers and virtual machines (VMs) are both isolated virtual environments that are used to make software. People use Docker containers because they are lighter, faster, and more resource-efficient than virtual machines.