Could you walk through the big picture again, like how mypysql, flask, http, apache all work with each other?

Could I get a sentence to put all these topics together? Like how do static pages relate to templates, and how do HTTP methods and URL building relate in the whole picture?

Does the url_for() method have to point to a specific file or folder to work properly? 

Are all functions for urls located in one python file?

What do you mean by 'always' use redirect(url_for())?  Should we use it in the place of render_template()?

I don't think I understand what a static webpage is - how do I know if my html file is static or not? 

Can you go over static files and templates with variables? When using render_template are we creating the static file? 

Retrieving POST data is "getting" data using request.form but different from retrieving GET data (request.args)? Why doesn't GET retrieve the POST data?

I'm confused by templates. I still don't really understand why templates are useful. Also, for the examples, I understand that the functions are using the corresponding templates, but I'm unsure as to what the functions are trying to accomplish. 

What is caching and why does it matter that POST doesn't cache? What are line statements (delimited by # ... ##)?