Here's an explanation right from their site:
File Sync
Dropbox allows you to sync your files online and across your computers automatically.
- 2GB of online storage for free, with up to 100GB available to paying customers.
- Sync files of any size or type.
- Sync Windows, Mac and Linux computers.
- Automatically syncs when new files or changes are detected.
- Work on files in your Dropbox even if you're offline. Your changes sync once your computer has an Internet connection again.
- Dropbox transfers will correctly resume where they left off if the connection drops.
- Efficient sync - only the pieces of a file that changed (not the whole file) are synced. This saves you time.
- Doesn't hog your Internet connection. You can manually set bandwidth limits.
Sharing files is simple and can be done with only a few clicks.
- Shared folders allow several people to collaborate on a set of files.
- You can see other people's changes instantly.
- A "Public" folder that lets you link directly to files in your Dropbox.
- Control who is able to access shared folders (including ability to kick people out and remove the shared files from their computers).
- Automatically create shareable online photo galleries from folders of photos in your Dropbox.
Dropbox backs up your files online without you having to think about it.
- Automatic backup of your files.
- Undelete files and folders.
- Restore previous versions of your files.
- 30 days of undo history, with unlimited undo available as a paid option.
A copy of your files are stored on Dropbox's secure servers. This lets you access them from any computer or mobile device.
- Manipulate files as you would on your desktop - add, edit, delete, rename etc.
- Search your entire Dropbox for files.
- A "Recent Events" feed that shows you a summary of activity in your Dropbox.
- Create shared folders and invite people to them.
- Recover previous versions of any file or undelete deleted files.
- View photo galleries created automatically from photos in your Dropbox.
Dropbox takes the security and privacy of your files very seriously.
- Shared folders are viewable only by people you invite.
- All transmission of file data and metadata occurs over an encrypted channel (SSL).
- All files stored on Dropbox servers are encrypted (AES-256) and are inaccessible without your account password.
- Dropbox website and client software have been hardened against attacks from hackers.
- Dropbox employees are not able to view any user's files.
- Online access to your files requires your username and password.
- Public files are only viewable by people who have a link to the file(s). Public folders are not browsable or searchable.
Check it out at http://www.dropbox.com/referrals/NTEwOTk3OTI5OQ
