It's more like this: you and I have some process we're collaborating on, and we both have an interest in getting accurate outputs from some kind of computation related to that process. But the only way to get really accurate outputs is to feed in proprietary, "secret" data from both your company and mine, and while we both have an interest in those outputs, neither of us wants to share our proprietary data with the other.
This solves that problem by letting us each put our data into our own Excel workbook, mine visible only to me and yours only to you, and then get the output of some mutually-agreed-upon calculation using both of our inputted data, without ever seeing the numbers the other party put into their workbook. So if you and I can agree on formulas that would provide the outputs we want, and I trust you to enter accurate data on your end and you trust me on mine, we can now do a lot of interesting analysis without ever having to open our respective kimonos, as the saying goes (http://www.npr.org/sections/codeswitch/2014/11/02/360479744/...).
I have no idea how well it actually works, or how secure the data flowing between the workbooks actually is. But it's an interesting idea!