Power Point slides updating automaticaly

Not sure where to put this post so I picked General. Don't scream at me!

So everyone has heard of or seen digital signage. Recently I ran across something and I can not figure out how it being done. A business that I visit has something that looks like digital signage but its only power point. This is good so far and I understand how this is being done, no problems. However, what they have done is wrote something in the power point slides to go out and grab information from spreadsheets (or other places) and update the slides while they are live! This is my problem, how are they able to update a slide pack while the slides are set up as a show and running live? Not only does it grab data, it is also grabbing random images that I am sure are contained in the spreadsheets.

Someone talk me through how this is being done please!