Emulated devices, also known as device emulators, are mobile operating systems running on non-mobile devices. Most developers use device emulators on their laptops to test their products on different devices or operating systems without the need to go out and purchase and setup all different devices. A developer might want to test their app on iOS 9, 10, and 11 on the iPhone 7, 8, and X without having to purchase and set up every device. Another functionality that applies to these devices is that you can set them up to perform actions programmatically without needing a human to execute tasks.
These emulated devices can be abused in the mobile ad space. Fraudsters will use scripted emulators to repeatedly interact with your paid ad campaigns, install your app, and execute conversions in attempts to steal your ad spend.