what is difference between VM (virtual machines) vs Containers

Virtual machines

• Specialized software, called a hypervisor, emulates the PC client or server CPU, memory, hard disk, network, and other hardware resources completely, enabling virtual machines to share the resources. The hypervisor can emulate multiple virtual hardware platforms that are isolated from each other.

Containers

• Instead of virtualizing the hardware stack as with the virtual machines approach, containers virtualize at the operating system level, with multiple containers running atop the OS kernel directly. This means that containers are far more lightweight: they share the OS kernel, start much faster, and use a fraction of the memory compared to booting an entire OS.

Conclusion:

These days containers are the most popular technologies used in DevOps, like docker and kubernetes