Dropbox is a piece of software you install on your computer, that any file placed in that folder is automatically synced with Dropbox.com as well as any other computers/cell phones/etc. linked to the account. (When I say etc. I really don't know what else you could sync it with.)
It's as simple as that.
There area few other little things that are awesome, such as saving things to your Public folder, such as pictures of your D2 or WoW items you're selling, right clicking on the file/image and clicking in the context menu, "Copy Public Link":

OH, an AWESOME thing about the Context menu this has, it ONLY appears in your Dropbox folders, so it isn't all over the place like SOME programs like to do.
That and it keeps deleted files, or previous version
s of CURRENT files or even deleted files, which you also have the option of making that disappear if you really want o also, for whatever reason.
You can also share folders with other Dropbox users you know if you'd like, and it will automatically sync that folder with both people after. (This does use your space.)
The speeds, syncing up or down are great, but if the other computer is on the same network, on the same linked account or folder, it will send the folders/files over the network rather than download/upload/etc..
Of course, you can always login online and upload or download any file incase you aren't on a computer you want Dropbox on, such as at school or a friends place.
You start with 2GB of space, doing the, "Getting Started" gives you 250MB more and signing up through my referral link:
https://www.dropbox.com/referrals/NTU0MzM3MDg5Also when you make referals after you have an account, you get 250MB more, upto 8GB extra.
So for free, you can have a total of 10.25GB.
You can also do photo galleries, if you want.
I won't lie, I'd love to have some referals, but mostly, I just wanted to say this software/FREE service saves my life every single day, and it shouldn't be a secret from jsp folk.
OH, you can disable ALL notifications. HOORAY!