Complex sentence: The Dropbox client enables users to drop any file into a designated folder that is then synchronized with Dropbox's cloud-based service and to any other of the user's computers and devices that also have the Dropbox client installed.
Split into simpler sentences: The Dropbox client enables users to drop any file into a designated folder. The file is then automatically uploaded to Dropbox's cloud-based service and made available to any other of the user's computers and devices that also have the Dropbox client installed.