A wildly brief overview, since the online docs and guides are incredibly good.
Docker is a tool to help us build and ship applications
Download / build Images
Create Containers based off of images
They’re not VMs
They’re not “lightweight VMs”
Google is your friend here
docker images
lists information about your imagesdocker ps
Lists information about your containersdocker run
Runs an imagedocker run docker/whalesay cowsay Howdy
runs the whalesay imagedocker run -it busybox
runs the busybox image in interactive + pseudoterminal mode