How I Use It
I used it to keep documents off of my home computer to save space. I also used it so I didn't have to email documents between home and school or carry a flash drive. You could also use it as a place where students submit their digital work to you, but again, as mentioned above, I would definitely prefer Google Drive for this.
Dropbox is an online substitute for a flashdrive or saving documents, pictures, anything to your computer. By saving to Dropbox, you can access all of those files from any computer. When you sign up, you do get limited free space, and in order to get more space, you have to pay (a lot) or can invite others to join. Dropbox is nice because you can have a desktop icon on both your school computer and your work computer and when you save a document in one location, it will automatically update in the other location. I no longer had to carry a flash drive between school and home. I loved my dropbox until I switched to another school district. At my new district, we are not allowed to put anything on our desktops, so Dropbox doesn't seemlessly upload like I liked. My dropbox also got so full, it was jammed stuck for many months which was incredibly frustrating. There was no one to contact to remedy the problem. It was perpetually syncing. I no longer use it. Now, it just makes so much more sense to use Google drive. Everything automatically syncs, you don't have to download shortcuts to your desktop, and you can collaborate.