Dropbox is an online file sharing service which allows users to store and access their files (documents, photos, videos, etc.) securely from any computer, tablet or smartphone. Access is private by default, but files may be shared with coworkers, friends, and family if they have the password. Dropbox comes pre-loaded on some phones, and was at one time blocked by the Chinese government (both of which are testimonials to its usefulness).
The company came into being largely due to founder Drew Houston's dissatisfaction with existing data storage options while a student at MIT. According to Dropbox's website, they have reached over 300 million users, and the service now works with Windows, Mac, Linux (including ChromeOS), iPad, iPhone, Android and Blackberry.
Dropbox is what is often called a "freemium" service, with basic users receiving 2 GB of storage space at no charge, and a greater amount of storage (and other services) with a paid account. For the basic service there is no limit on individual file size, but the total daily traffic from all links is 20 GB (a higher traffic rate than this can result being banned from the service). The traffic limit for Pro and Business accounts is 200 GB per day. Dropbox synchronizes files changes on all linked devices, but there is version control, so earlier versions of the files can be recovered. This is one of many features which makes Dropbox such a useful tool for collaborative work. Version history is kept for 30 days in the basic account, but an unlimited version history is available for purchase. Files are available even if you are offline, and if something happens to a linked device the files can be recovered from the cloud. Dropbox, incidentally, takes measures to prevent sharing of copyrighted material (unshared documents in an individual's Dropbox folder are not subject to these measures).
There are many official and unofficial add-ons for Dropbox which can enhance functionality. MacDropAny, for instance, automatically syncs any folder on a linked device to Dropbox. There are also client applications for operating systems which Dropbox does not officially support, such as Maemo, Windows Phone, Symbian, and WebOS. In addition to these add-ons, Dropbox regularly makes improvements to the usefulness, speed, and reliability of its service.
Dropbox for Business is a for pay service which implements separation of business and personal documents (administrators cannot see personal documents), as well as restrictions on sharing in order to prevent accidental disclosure of intellectual property. Dropbox for Business also allows other administrative controls and auditing capability for IT departments. Different types of files can be stored in different cloud containers yet still be viewed side by side with this paid service.
Dropbox has received good reviews from The Economist, The New York Times, PC Magazine, and other publications, largely due to its simplicity and how easy it is to use. It is by and large a non-problematic service.
Dropbox widely used in many businesses the computer guy services and even more households. I use it and it's highly recommended. You can download it at www.dropbox.com and it's really easy to sign up for it.