Many of the ESP32 modules use a dual core version of the ESP32 processor.  This allows one of the cores to run the all the multitasking involved in updating the WiFi stack etc and the other for your main applciaiton carrying out all your data processing and IO.

The two cores:

Protocol CPU (PRO_CPU)

Handles WiFi, Bluetooth and other internal peripherals like SPI, I2C, ADC, etc.

Application CPU (APP_CPU)

Your application code

The differentiation is done in the Espressif Internet Development Framework (ESP-IDF) which uses freeRTOS for switching between the processors and data exchange between them.

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