SDR
Software-defined radio (SDR) is a system where conventional analog electronic hardware is implemented by means of digital software algorithms on a computer.
https://en.wikipedia.org/wiki/Software-defined_radio
The rapidly evolving capabilities of digital electronics render practical many processes which were once only theoretically possible.
https://en.wikipedia.org/wiki/List_of_software-defined_radios
RTL-SDR
Inexpensive USB dongles with the Realtek RTL2832U controller and tuner, e.g. the Elonics E4000 or the Rafael Micro R820T can be used as a wide-band (2.4 MHz) SDR receiver.
https://www.nooelec.com/store/sdr/sdr-receivers/smart/nesdr-smart.html
https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
ADALM PLUTO
12-Bit Software Defined Radio – 5mW Full Duplex – Ethernet or USB – Multi-Band – 2 Meters to 23 cm – 70Mhz to 6Ghz
https://wiki.analog.com/university/tools/pluto
https://github.com/analogdevicesinc/plutosdr-fw
HackRF One
In a category all by itself:
https://greatscottgadgets.com/hackrf/one/
Software:
SDR# (SDR Sharp) by AirSpy
The best free SDR software for Airspy, Hack RF, and RTL-SDR dongles!
Only for Windows.
https://airspy.com/download/
https://www.rtl-sdr.com/sdrsharp-plugins/
SDR++ (SDR Plus Plus)
The best bloat-free cross-platform open-source SDR software!
Windows, Linux, OSX, and BSD operating systems.
https://www.sdrpp.org/
https://github.com/AlexandreRouma/SDRPlusPlus/releases
SDR Touch
Allows use of an RTL-SDR, NeSDR, SDRplay, or HackRF SDR on Android Devices with USB-OTG support.
https://play.google.com/store/apps/details?id=marto.androsdr2
RFAnalyzer – (Deprecated)
Use an OTG (on-the-go) USB cable to connect your HackRF/RTL-SDR to an Android phone/tablet and visualize the RF Spectrum.
https://play.google.com/store/apps/details?id=com.mantz_it.rfanalyzer