Docker is a virtualization software that deploys docker containers. Due to easy handling and reproducable environments it is a useful tool.
pacman -S docker to install dockerTo run docker as a non-root user you need to add your user to the docker group.
To do this create the group docker if it doesn't exist sudo groupadd docker
and then add your user to the group using sudo usermod -aG docker $USER.
After that relog into your machine and you should be able to run
docker run hello-world.
To use Nvidia GPUs with docker you need to install the nvidia-cuda-toolkit. There is a guide on marmelab that focusses on that topic.