Go over to the official Docker page at https://docs.docker.com/compose/faq/

Docker is 100% free. It is open source, so you can use it without paying.

Containers have similar resource isolation and allocation benefits as virtual machines but a different architectural approach allows them to be much more portable and efficient. Docker containers run on virtual machines. With a virtual machine, the server includes the application, all the binaries and libraries and an entire guest operating system which may be massive. […]

Docker allows you to package an application with all of its dependencies into a standardized unit for software development. Docker containers wrap up a piece of software in a complete filesystem that contains everything it needs to run: code, runtime, system tools, system libraries – anything you can install on a server. This guarantees that […]

Agility Docker gives developers the freedom to define environments, and create and deploy apps faster and easier, and flexibility for IT ops to quickly respond to change. Control Docker enables developers to own all the code from infrastructure to app, and the manageability for IT ops to standardize, secure and scale the operating environment. Portability […]