These are really two different content types but for the user maybe we should call them "page types"? We want to emphasize that there are pages for more than one piece of content (an index) and pages for a single piece of content (a post).

I would begin explaining themes to the user something like this:
```
Themes are written using Closure Templates. They become functions that are called by Lisp with the blog data and output HTML. Since the Lisp code to use the theme is already written, your theme must follow a few rules.

There must be three templates which handle specific arguments/variables (to be described later).
1. Base
2. Index
3. Post

Also, those templates must be in a folder under "themes/" named after the theme, each starting with a namespace declaration like so: {namespace coleslaw.theme.$MY-THEME-NAME}
```
It's worth noting then that the easiest way to create a theme is to copy an existing one outright, change the name and namespace declarations and mess around with the CSS, reminding them that the CSS only gets copied if it is in the theme/*/css directory.