WHAT THE HELL IS A DROPBOX

So . . .  What the hell is a "Dropbox" and why is mine ALWAYS "almost full ?

For the past year or possibly two EVERY time I turn on my computer a little message appears in the top right corner of my screen stating "Your Dropbox is almost full".   Oh Really ???    . . .   And what the hell am I supposed to do about that ?

First off, I have no idea what a dropbox is nor do I know where it came from.  It is not something I chose to install on my computer yet it magically appeared several years ago and some how or other someone seems to be filling it up when I'm not looking.  I have no idea what the dropbox contains nor do I care unless it is filling up with hundred dollar bills. If that is the case I would like to know how to find it and how can I get everything out of it.

The even bigger question in my mind is how can it be "ALMOST" full for an entire year? If stuff got dropped into it a year ago where did that stuff come from? Did things get dropped in there for a two week period and then stop just as quickly and mysteriously as it started ? Why did it start filling up in the first place?   AND why did it stop filling up at ALMOST full and not just continue accumulating junk until it was FULL?

I can understand that when this phantom box was 3/4's full it would send me the "almost full" message. But then wouldn't you think that if I didn't do anything about it the damn thing would eventually fill up and I would get a message saying,  "Your dropbox is FULL" ?

These are the things that keep me awake at night . . . If only I had a little cyber box that I could dump all these crazy thoughts into . . .