What possibilities exist so websites basically build automatically? [on hold]

What possibilities exist so websites basically build automatically?

An example, let's say I make an HTML file by scratch and style it with CSS and that locally on a PC. I would need to change everything (navigation and etc.) on each file if I modify it on one.

And that can be annoying.

 

So I want to ask, what possibilties do exist so I can prevent that "work"?

 

I know that WordPress is something that gives the possibility to do that, never really used it from scratch so, don't know. I think you have a bunch of templates, and create a navigation bar and assign that to a template that you embed in each site and so on and so on.

But what other things exist?