It’s a low friction way to set up a home server with NAS and docker containers. The “Unraid” portion is the configuration that lets you set up an “array” with parity drive(s), but without striping so each disk has a complete filesystem and files accessible even when removed from the array. Everything can be managed through a web UI, and there’s a robust “app store” of docker containers.

The downside is that it’s not free, and they recently moved towards monthly/yearly licensing and increased the cost of new lifetime licenses.