VMs have the host OS and guest OS inside each VM. A guest OS can be any OS, like Linux or Windows, irrespective of the host OS. In contrast, Docker containers host on a single physical server with a host OS, which shares among them. Sharing the host OS between containers makes them light and increases the boot time. Docker containers are considered suitable to run multiple applications over a single OS kernel; whereas, virtual machines are needed if the applications or services required to run on different OS.
https://cloudacademy.com/blog/docker-vs-virtual-machines-differences-you-should-know/
https://velog.io/@kdaeyeop/%EB%8F%84%EC%BB%A4-Docker-%EC%99%80-VM%EC%9D%98-%EC%B0%A8%EC%9D%B4
https://blog.mikesir87.io/2017/05/docker-is-not-a-hypervisor/
