Docker is a method of virtualization on an application level.
You host a container platform on your computer and this allows you to utilise containers.
Example of Containers are applications such as
Plex
Sonarr
Pihole
Each container is a ‘complete’ platform with all the dependencies included - your container platform supplies Disk/CPU/Ram and network for the Container to function.
Containers can be based on operating systems that are different to your computer.
Using containers mean you have a very easy way of trying an Application without installing to your native operating system.
Let us know if you have a NAS /PC /Server and we can tailor the answer further.
This guy fibers!