what is "-it" docker code example

Example 1: what is docker

Docker is a set of platform as a service products that use OS-level
virtualization to deliver software in packages called containers. 
Containers are isolated from one another and bundle their own software,
libraries and configuration files; they can communicate with each other
through well-defined channels.

Example 2: docker container

docker container ls -a
docker ps -a

docker container stop [ID]

docker container run -d -p 80:80 --name nginx-server nginx