Docker image before development or after? (Beginner)

I am trying to build a website with Node.js and Socket.io with HTML5 canvas. I am new to docker and containers and am trying to understand how they work. I have a couple of questions that I would like help understanding.

1. Should docker be installed before development of the application or after?
2. Can I deploy docker on a Mac?
3. How to setup the environment to use the technology?

Questions may be naive but I am a beginner. I researched on google and most articles explain what docker is and how is it better than VM but not many show the usage or how-tos. Any leads would be appreciated.