The Dropbox (document-sharing) tool provide a place where users can leave files for each other, to be downloaded as convenient, avoiding heavy e-mail downloads. Files can be “dropped” there by the teacher for learners to collect, by a learner for other learners (if allowed by the platform administrator) or by a learner for the teacher (although it is not really intended for the delivery of homework or assignments, for which the Assignments tool should be used.)
While the basic concept of this tool is similar to popular tools such as Dropbox or Google Drive, it actually predates these modern tools and doesn't work in quite the same way. For example, when working collaboratively on one document, rather than open the “shared” file to view and edit it directly users simply download the shared file, work on it, and upload it again to the dropbox (e.g. with changes). By default, altered files won't over-write the original version even though the filename is the same, effectively making it easy to manage “versions” of a document differentiated by date/time of upload. All users have the option to add a comment within the dropbox window to a shared document, again a useful device for serious collaborative work. For example, it allows a teacher to make a brief note about each student's contribution.