It's basically a bunch of different transmitters/receivers packed into one device.
On the legal side, you can use it as a hardware token, to store NFC/RFID/Infrared/Bluetooth/etc data and transmit it as needed (for example, as a garage door opener, as a universal TV remote, to unlock your car, or to store your credit cards for wireless pay without having to use GPay or some other app shit).
On the not so legal side, you can use it to sniff/crack Wi-Fi, hack into any number of digital signs in the outside world (because most of them never have their default passwords, or even fuck with Teslas by opening the charge port.
It can do a lot more than what I've listed but that's just the very basic overview of what it can do. I've seen/heard of some creative uses for this device, especially useful if you're skilled in programming for embedded devices and working with electronics.