A Container Beside a Virtual Machine

Both hand you something that behaves like its own machine. They buy it differently, and the difference is what decides which one you want.

The same job, paid for two ways
Compared on	Container	Virtual machine
What starts	A process	A kernel, then an init system, then your process
How long	Milliseconds	Tens of seconds
What separates it	Kernel features, on a shared kernel	A boundary drawn in hardware
Can run another OS	No, the kernel is the host's	Yes

Reach for a container when you want the Linux you already have, packaged so it runs the same on someone else's machine. Reach for a virtual machine when you need a different kernel, or a boundary strong enough to put someone you do not trust behind.

Docker
Containers