A collection is a series of small items that you wish to communicate about. This isn't limited to things in this site as it's typically a way of showcasing work or linking off to resources. This design can also be used as a template for making small showcases of work and adding additional pages into the mix.
Users will click on items in the list to jump off to pages elsewhere. You could use this to link to a portfolio of work, an index of content created that is non-linear, showcase work, or anything you like! This is just boilerplate to generate ideas!