Circles adds a drop area to the left side of your screen, you can either drop content onto a Circle to open an application with it, copy or move it to destination, you can also drop files into the Drop Area by dragging them in to store them for later, or to share between other apps.
You can setup up to 4 Circles which can perform actions such as:
- open app, open with app
- copy to destination
- move to destination
Or drop content into the middle Wormhole circle to add them to your Drops Collection. Once done, you can simply drag them out and drop them into other applications. Circles isn't a new idea, it just closes the issue created when its origin app dropped the feature in its last major release... Circles isn't designed for pro usage, so there is no way to upload or do other stuff: there are other apps out there doing this better. Circles is for the more common tasks, extending the Dock, rather than reinventing any features...