Permission required: Curate
Under the Curate tab, you'll see the locations where each collection is currently published in the "Mapped to" field of the "Published collections" grid.
In the left sidebar, you'll also see links that represent each location on your site.
Click these links to see the collections that are currently published in each section of your site. From here you can also see the order of collections in that section (and rearrange collections, if you'd like).