You won't use Docker until much later in the course, but it is required to be installed.
Just visit docker.com and download and install the latest version of Docker Desktop. Docker for Windows requires WSL 2 to be already configured and working.
Installing Docker on Ubuntu Linux is a little more involved, as there isn't a download on the main docker page. Docker does have an easy-to-use convenience script that will install docker for you using curl.
You can read Install using the convenience-script for more info about this.
But it involves running these commands:
curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh get-docker.shThen, in order for you to be able to run the docker commands without using sudo
you should run this command, replacing your-user with your linux user name. Remember, you can type whoami to find out what this is.
sudo usermod -aG docker your-user