The processor in the Raspberry Pi Pico, the RP2040, has a feature called PIO - Programmable Input/Output. As a result you have access to 8 little processors with their own assembly language which you can program to create deterministic interfaces to the real world.
The Pico's PIOs are programmable like general processors. The 8 state machines processors can independently execute programs to manipulate GPIOs and transfer data.
RP2040 Datasheet (look for Chapter 3: PIO): https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf
Pico MicroPython Examples: https://github.com/raspberrypi/pico-micropython-examples/tree/master/pio
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