You’ve heard the term “SDR” Software Defined Radio, it seems to be a catch-all term for anything managed by a circuit board with “Smart” (Programable) parts. When we discuss this in Amateur Radio or Shortwave listening it can be a transceiver (Transmitter/Receiver) or Receiver.
there are many flavors from USB dongles that require an external computing device to full sized self contained radios that have their own internal processor and possibly a video display. These devices can have wildly varying prices from a few dollars to thousands.
Lets start with a RTL-SDR USB Dongle
The RTL-SDR website includes a link to Software support by this device and Many others we’ll list on this site
USB Spectrum Analyzers by Signal Hound (and you thought your transceiver was pricey!)
SDRplay my personal favorite
SDRplay and many of the SDR receivers can be purposed as a “spectrum Analyzer” using specific software and working within the limits of the device.