I am new to website building so I have a question about templates and css. I am not using a template to build my website, I am creating it from scratch and using an external stylesheet. But what I am wondering is whether or not I need to create a template or not too. Once I get the layout the way I want it do I need to make it into a template and then create my pages based off my template, which will include the stylesheet? Because say I don’t create a template and later I decide to change the logo image or something like that, would I have to go and change ever page to have the correct logo or can that be done with css?
Sorry, I am just a bit confused about the necessity of templating during creation. 
If you’re writing your own stylesheets, using the word ‘template’ might not be quite appropriate.
CSS can (and should) be used to control every aspect of presentation, layout and styling of a web page. You’ll create a framework of HTML that ties in with the CSS. You can then use this as a ‘template’ and add the relevant content to it to make each page. (Or do what many people do, which is to open an existing page in your editor, save it under a new name and change everything that needs to be changed - the end result works out the same)
You can then make global changes to the CSS, which will affect every page that uses that stylesheet. If you’ve set your HTML framework up properly, that should give you more or less free rein to change the design however you want.