A Panadapter is know by many names. The most scientific and correct might be “radio spectrum scope”, but the most common in the ham sphere is “panadapter” or “pan-adaptor” in my short experience. Basically, it’s a wide panoramic view of a radio spectrum.
For a ham, it’s normally used in conjunction with a transceiver or a set of transceivers. It’s also common that the computer doing the spectrum visualization is connected to the transceiver via CAT or similar, so that a click in the spectrum view tunes the transceiver to the desired frequency.
To achieve this you can invest in really expensive SDR hardware, or you can go this route (amongst others), which I did with my Kenwood TS-570D: