This category includes two types of radios:
Conventional superheterodyne radios controlled by software, with either a minimal or no front panel human interface. Signal detection/demodulation is done in hardware/firmware, with "software defined" techniques generally applied only on the last IF. Examples:
Software Defined Radios (SDR). All signal detection/demodulation is done in software. Examples I have used include:
AFEDRI SDR-Net (Ethernet capable, network SDR clients support Windows, Linux, MacOS)
RFSpace Cloud-IQ (network SDR clients support Windows, Linux, MacOS)
SDRPlay, 12/14-bitSDRs, 100 kHz - 380 MHz, 430 MHz - 2 GHz, with support for Windows, Linux, MacOS, Rasberry Pi, and Android
Software Radio Laboratory LLC QS1R (My favorite, receives 7 bands at once, and supports Windows, Linux, and Mac)
KiwiSDR network accessible SDR with web browser interface.
Shortly after the year 2000, a number of specialty chips were developed to support new digital television standards, DVB-T (Europe, Africa, Asia) and ATSC (North America, South America and South Korea). Eventually radio, hardware, and software hobbyists figured out how to repurpose these chips for use as general purpose SDR communications receivers. These chipsets have enabled the production of very inexpensive, yet capable, radios.
One of the earliest and most popular series of such SDRs are the many variants of RTL-SDR. These are based on a variety of chips such as RTL2832U ,Elonics E4000, Rafael Micro R820T/R860/R828D, FitiPower FC0012/FC0012, and the FCI FC2580. Many RTL-SDRs are implemented in the USB-dongle form factor, similar to a USB memory stick. The basic chips have 8-bit analog-to-digital converters, which does limit their dynamic range. More detail about RTL-SDR can be found at RTL-SDR.COM.
Another popular digital Radio/TV chipset from Mirics Semiconductor, the MSi001 tuner chip and the MSi2500 USB interface/ADC chip, are used in the SDRPlay series, the FUNCube Dongle Pro+ and many Chinese "MSI-SDR" or "RSP1" clones.
While many black box radios are much smaller and lighter than conventional and boatanchor radios, they do require the use of a separate computer (desktop, laptop, tablet, phone) to control them.
My favorite radios support open application programming interfaces and/or front ends that support multiple operating systems. With the Qt framework, there's really no excuse for single-operating system SDR front ends.