I have 2 desks in my office, both with multiple screen layouts. Your question made me think about how I use them and it comes down to the task I am performing.

Like others, when I am programming I typically have an IDE where I am doing work on one and a reference open on another. When doing web development my third monitor usually has a browser where I can immediately refresh my work to see results, for other development it may be a virtual machine or remote desktop that I am logged into.

When I am doing academic work, I often have EndNote (reference manager) on one monitor, the document I am writing on another and the documents I am finding / reading on the third.

Since both my desks are next to each other, I often "borrow" a monitor from the other setup to keep communication windows open (Skype, Lync, Hangouts, #Slack etc.) This allows me to keep in touch with coworkers and colleagues without having to flip windows every time I get a message.

So I would say there are three purposes identified:

• Active Work
• Reference Material
• Communication