Asking about CMS implementation

I've been learning web development for some time now, and I can't figure out how does CMS work. Let's say I have coded a website in html, css and javascript and now I would like to make it easy for me or for other people to edit content there. Is it possible to insert a script which will do the work for me or do I have to learn for instance python? I am interested in the process of going from front-end web development to creating a CMS.