What Does the EN Pin on the Header Do?

The EN pin is tied to the 3V3 LDO on the board. When the pin is pulled LOW (pulled to GND) it shuts down the LDO, which in turn shuts down the 3V3 power rail and anything connected to it, like the ESP32 chip.

By default, the EN pin is pulled HIGH, which enables the LDO.

For boards with dual 3V3 LDOs, the exposed EN pin connects to the primary LDO.