I recently got an ESP32 development board. I also found the schematic to this board online but I got an question. Can someone explain to me, what this part of the circuit is doing?
EN is enable... Or nrst pin. IO0 is a boot mode pin. When the esp32 chip exits reset, it samples io0 and if it's low it will enter programming mode.
This enables the dev board to reset the board and automatically select the correct values for those pins when programming. See: https://github.com/espressif/esptool/wiki/ESP32-Boot-Mode-Selection