In terms of technology, real estate generally refers to the screen size of your monitor and the subsequent size of your desktop—in other words, the amount of space you have to see what you need to see.
Several years ago, I went from a single monitor to two monitors. Whoa!! I loved all the extra real estate. I could have at least two things open at once and be able to see them both at the same time. That’s especially helpful if you need to see one program or document in order to work on the other. Flipping between programs is royal pain.
Now, my boss has four monitors, two stacked on top of two. That’s a bit much for me. Of course, his are square and the combined height is too high for me to comfortably be able to look up at. My monitors are rectangular (horizontally), so I guess another row of them wouldn’t be so bad. But for what I do, I’ve never really wished I had more. I suppose your needs depend of your line of work and how many programs you juggle at any given time.
Remember, though, that you may need a special video card to support two (or more) monitors, so do your research before embarking your purchases!