Default CSS - This version of Foundation includes smart defaults and doesn't require Sass or any other tools. Everything in this is minified, so you would use this to build on top of Foundation.
Custom CSS - You can customize your build of Foundation below to include or remove certain elements, as well as to define the size of columns, colors, font size and more.
Sass + Compass - Foundation is built using SCSS, and you can work with it in the same way. To get Foundation using Sass and Compass, check out the instructions on the Install documentation page.
This label could read a date for an update, or it could include an author name, or anything really. Inline labels are pretty handy when you need to draw attention or visually separate a short piece of content.