Dropbox is a service that allows you to synchronize a special folder on your computer with storage online, as well as to synchronize that folder to folders on other computers you own.
The Dropbox service gives you 2 gB of storage free, and you can upgrade to higher levels of storage for a fee.
We use Dropbox all the time to send large files to clients and for collaboration over a distance. When you sign up for Dropbox there are several online help presentations that will let you understand all of the things that it can do.
If you sign up for Dropbox using a referral link, you automatically get an extra 250mB of space (and so does the person whose link you used. If you sign in with this link http://db.tt/wq6ynrb you'll get some extra space right off the bat and so will I - thanks.
If you prefer not to use that link, or just want to poke around the Drobox site to learn more, visit them at http://www.dropbox.com.