Sections: A group of Exhibits (e.g. the bold headings on the lefthand side "Indexhibit Basics", "Exhibition Formats")
Exhibits: a page representing a work. Can contain text, images and links and is a child of a section. (e.g. this page "Getting Started: Tour and Definitions" is an exhibit)
Exhibition Options: on an Exhibition Edit page, click to see your options for the chosen Exhibition Format (i.e. things like whether your thumbnails are square or rectangular, or whether your description text will show up to the left or right of your images). The options will be different for every Exhibition Format
Preview Button: on the Exhibition Edit page, click to see what the exhibition will look like on the front-end before actually publishing your changes
Refine Button: when you are Previewing your Exhibition click this to open the Exhibition Options and tweak the look while you're viewing it