A standard box is likely the most common box type you'll use, as it allows you to add assets and Rich Text/HTML content to your pages. A standard box is flat, in the sense that the content you add displays directly on the page. This is in contrast to a tabbed box, which allows you to divide content in the box across multiple tabs. For adding simple content to your guide, therefore, a standard box is always a good option as it will give you the simplest layout.
One way to customize the appearance of your guides is by customizing the styles and colors of your content boxes. Want border-less boxes? Squared corners instead of rounded? Blue box headers instead of gray? These are just a few things you can do in your guide's Tab & Box Options. Tab & Box options can be set at three levels: