Docker and Virtual Machines (VMs) are both technologies used for virtualization. The main difference between Docker and VMs is that Docker provides operating-system-level virtualization, while VMs provide hardware virtualization.
Docker is a containerization technology that packages an application and its dependencies into a self-contained unit that can be run on any Linux-based server. This allows for applications to be quickly deployed and run on any host, regardless of the underlying operating system.
A Virtual Machine, on the other hand, is a software program that emulates a physical computer. It runs on top of a physical machine, and provides a complete virtualized hardware environment for the guest operating system to run in.
For example, if you wanted to run a Windows application on a Linux server, you could use a VM to run the Windows environment on the Linux server. This would allow you to run the Windows application without having to install Windows on the server.
In contrast, if you wanted to run a Linux application on a Windows server, you could use Docker to package the application and its dependencies into a self-contained unit that can be run on any Linux-based server. This would allow you to run the Linux application on the Windows server without having to install Linux on the server.