Docker is an open source project designed to help with application deployment using software containers. This approach means running applications together with the complete environment (files, code libraries, tools, and so on). Docker, therefore—similar to virtualization—allows an application to be packaged into an image that can be run everywhere.
Without Docker, isolation and other benefits can be achieved with the use of hardware virtualization, often called virtual machines. The most popular solutions are VirtualBox, VMware, and parallels. A virtual machine emulates a computer architecture and provides the functionality of a physical computer. We can achieve complete isolation of applications if each of them is delivered and run as a separate virtual machine image.
The following diagram presents the concept of virtualization:
Each application is launched as a separate image with all dependencies and a guest operating system. Images are...