What is the difference between a Docker container and a virtual machine?

A Docker container is a lightweight and portable executable package that contains everything needed to run an application, including the code, runtime, libraries, and system tools, but shares the host machine's operating system kernel. In contrast, a virtual machine emulates an entire computer system, including the operating system, on top of a host machine's operating system.

The main difference between the two is that containers are more lightweight and efficient than virtual machines since they share the host machine's kernel and can start up and shut down faster. Additionally, containers are more scalable since they can be easily replicated and moved between hosts. On the other hand, virtual machines offer better isolation since they have their own virtual hardware and can run different operating systems on the same physical host.