What a beautiful piece of equipment!
This is a radio receiver. Properly set up it will scan from .005 MhZ to 3.335 GhZ. This tool will give you a clear idea as to what is going on in the electromagnetic spectrum around you. Scans can be set up, and an external speaker can be attached. Signals that you recognize can be ignored, and you can look for suspicious signals that pop up.
If you have something around you that is transmitting, something that you did not know about, then this might represent an invasion of your privacy. A device like this can be used for many purposes. The one pictured here is extremely sophisticated. Others are simple and cheap. The purpose of this device is not to do a technical survey of a room or series of rooms. It would only be able to find rudimentary listening devices. Its purpose is to see a big chunk of the spectrum as to what kinds of transmissions are going on in your area. Although it is true that this receiver would pick up a radio signal coming from your computer if that signal was between .005 MhZ and 3.335 GhZ. If your computer is sending out a radio signal (with your information) that you do not know about, then it is time to get a new computer.
This receiver will pick up all kinds of traffic: am radio, HF signals, aircraft, push-to-talk radio, commercial radio, digital signals of many kinds, analog television (audio), encrypted signals (they will only be seen and a garbled noise will be heard), UHF radio, emergency beacons such as avalanche or downed-aircraft locating devices, etc.
The next step is learning about the electromagnetic spectrum and knowing how waves propagate and how they can be modulated. Learning about the spectrum tells you what kinds of signals are possible at certain frequencies.
One needs to be diligent because some signals only transmit at odd intervals or on unusual frequencies.
One must be aware of the legal aspects of using such a device. Laws vary, of course, by country. This device is passive, but one must be aware of, and follow, legal restrictions. Hobbyists use such devices all over the world, but they usually have sections of the spectrum blocked off. Make sure to follow your national and local laws.
There are many situations where a scanner like this would greatly enhance the security of a business or organization in hostile parts of the world, especially when this equipment is operated by attentive, competent personnel. Small scanners can also reveal enlightening information.