lol <3 I've already decided Felicity is going to 'speak in words others can understand' if she's ever asked to explain complex things idk anything about :D
In short, it's a map of electronic devices connected to the internet. It's often used by companies who make smart devices (tvs, fridges, ect) who want to see where their products are being used. Or as security for companies/people who need to be able to track their internet capable devices in the event they're stolen.
For IC applications, every time a device accessed the network, it would leave a dot on the map as a 'last known place'. They wouldn't know who owned each device (unless they want to go all Big Brother about it...) but they would get other data like where people outside the prison live and how many live in each place. Mostly Felicity would be suggesting it so they would know if any non-prison people were lurking around outside the prison unannounced. Or made a habit of hanging out close enough to watch them? And also so they would know the second any new device accessed the network, allowing them to pick up new people before they got eaten.