Pen-testing is short for penetration testing. Which is testing if you can break into the things. Like a locked office or a computer system, etc. Legally, it's done to find flaws that need to be fixed before they get used nefariously.

Pen testing techniques and tools are essentially break in tools. In this case, a tool for mimicking car key fobs and the wireless signals they send to the car.

Pen-testing: penetration testing, basically good guy hacking to find security vulnerabilities so that they can be fixed, basically finding out how easy a security system is to penetrate.

Debugging: fixing problems in hardware and software

RFID (Radio Frequency IDentification), radio, NFC (Near Field Communication,) infrared, Bluetooth: different forms of wireless communication.

RFID is used for stuff like security tags on merchandise, car key fobs

NFC is similar (you could probably make an argument that NFC is basically a type of RFID) with a very short range used for things like making payments with your phone

Bluetooth you're probably somewhat familiar with, in used for a lot of consumer electronics, wireless headphones, speakers, computer mice, etc.

All of those use radio waves in some form to pass information from one device to another.

Infrared uses a infrared light to send information, the most common use you've probably seen is for TV remotes, which is why you have to point the remote at the TV to work, you're basically flashing an invisible flashlight at the sensor on the TV

This device can basically mimic any of those kinds of signals allowing it access, control, or bypass devices and systems that use those protocols.

This can be useful for people working on those kinds of systems, you don't need to have the actual key card, remote, device, etc. to test it out, you can try a bunch of different configurations without needing to reprogram the card a bunch of times, and gives you a lot of options to test for different vulnerabilities and issues.

But those same capabilities make it attractive to people who would use it maliciously. If they don't have the right security measures in place, something like this device could be used to gain access to secure areas by spoofing a key card, unlock cars, interfere with cell phones, snoop on wireless communications, gain access to a someone's devices, etc.

It's basically a 2 way radio with tools for those who like to mess with the radio spectrum. That's the most simple explanation I can make for such a device.