If you are not running a newer operating system on Mac or Windows, then you will need to use Docker Toolbox. You may have noticed that the output from running the following:

$ docker version

On all three of the installations we have performed so far, it shows two different versions, a client and server. Predictably, the Linux version shows that the architecture for the client and server are both Linux; however, you may notice that the Mac version shows the client is running on Darwin, which is Apple's Unix-like kernel, and the Windows version shows Windows. Yet both of the servers show the architecture as being Linux--what gives?

That is because both the Mac and Windows versions of Docker download and run a virtual machine in the background, and this machine is running a small lightweight operating system based on Alpine Linux. The virtual machine is running using Docker's own libraries, which connect the inbuilt hypervisor for your chosen environment. For macOS, this is the inbuilt Hypervisor Framework (https://developer.apple.com/reference/hypervisor/) and for Windows, Hyper-V (https://www.microsoft.com/en-gb/cloud-platform/server-virtualization).

To ensure that no one misses out on the Docker experience, a version of Docker that does not use these built-in hypervisors is available for older versions of macOS and unsupported Windows versions. These versions utilize VirtualBox as the hypervisor to run the Linux server for your local client to connect to.

For more information on Docker Toolbox, see the project's website at https://www.docker.com/products/docker-toolbox/, where you can also download the macOS and Windows installers.