Dropbox

Dropbox is a simple solution for saving files to the cloud. With it, you can make the same files accessible across multiple computers by simply installing Dropbox on every computer that you use regularly and dropping files there.

This action enables you to sync files across computers with ease. However, a closer look at this program reveals that it's not suited to be used as a comprehensive online backup solution.

Online Backup

The Dropbox folder, which is conveniently placed on your PC's desktop upon installation, serves as the main graphical tool that connects you to Dropbox's servers on the Internet. Basically, for any of your files to be backed up online automatically, you need to copy/move/save them to the Dropbox folder.
While this may seem like a nifty tool, it also essentially means that if a program saves at another folder by default, files created through it will not be saved in the cloud.
One benefit of saving your files on Dropbox though is that you can revert to previous versions that have been stored in their servers up to a maximum of 30 days. What's more, if you upgrade to a paid version of Dropbox, that limit will be waived. That means you can perform an unlimited number of undos until you find the version you want to revert to.

File Sync

This is where Dropbox shines. If you start working on a Word document or Excel spreadsheet in your office computer and want to continue working at home, you simply copy your file to the Dropbox folder. Then once you arrive home, you turn on your PC, open its Dropbox folder, and that same file will be waiting there.
Unlike other web-based apps that require a constant Internet connection, Dropbox allows you to work even when you're offline. That means, if you're working on a laptop and you save the file in the Dropbox folder, you can still work on the same file even when you move to a location where you have no Internet access. Once you get back online, the system will automatically sync your file.
If you work within a local area network (LAN) and have Dropbox folders in different workstations, file syncing can take place much faster. That's because when its LAN Sync feature is enabled, Dropbox will only have to look for the newest copy of the file within the network and share it with other Dropbox folders found there. For this feature to activate, you'll need to be connected both to a LAN and the Internet.

File Sharing

Sharing files and collaborating with your team members can be easily done with this program. In just a couple of steps, you can already share files with existing Dropbox users. Non-Dropbox users will receive a registration invitation via email. After registration, they can then have access to the files you shared with them through their own Dropbox folder, allowing all of you to work on the same file at the same time even when you're all in your respective homes.
You can also specify who has access to which file or folder if you only want to share certain files with certain people. Files placed in the public folder, on the other hand, are viewable by anyone.
As for images, you can share them even with non-Dropbox users because they will be displayed in a gallery that can be viewed online. This is particularly convenient for non-Dropbox users who don't want to go through the registration process just to view your photos.

Reference: http://www.onlinebackupsreview.com/dropbox.php#ixzz1hPqYssNS