How do templates work

[steven-g]

I cannot find any useful tutorials on using templates and what a template actually controls. There is plenty of information on how to create a template.
I have created a template which I want to use for multiple posts, the test has an inner section with a heading and a text editor, I create a few posts giving them new text, and then go back and edit the template changing font color in the header and text editor, save the template and nothing changes in the created posts. Why? is this not what a template is supposed to do or am I missing something. A new post will indeed now have the new colors but existing posts keep the old styles.
Are you supposed to use some other workflow to control a sites syle.

 

[ChasUK]

As a beninner in all of this a useful question but no answers. Help please.

 

[Wheelz]

So when you create a template, you connect your fields using the dynamic options on the header, text area etc. Then you decide what post types you want the template to be used for using conditions which you get when you first save the template, or you can access by using the little up arrow at the bottom update button. It maybe that you have set the conditions to show the template on a post type or taxonomy that is only on some of your posts?