Datasheet

GND - this is the common ground for all power and logic

BAT - this is the positive voltage to/from the JST jack for the optional Lipoly battery

USB - this is the positive voltage to/from the micro USB jack if connected

EN - this is the 3.3V regulator's enable pin. It's pulled up, so connect to ground to disable the 3.3V regulator

3V - this is the output from the 3.3V regulator. The regulator can supply 500mA peak but half of that is drawn by

the ESP32, and it's a fairly power-hungry chip. So if you need a ton of power for stuff like LEDs, motors, etc. Use

the USB or BAT pins, and an additional regulator

Logic pins

This is the general purpose I/O pin set for the microcontroller. All logic is 3.3V

Serial pins

RX and TX are the additional Serial1 pins, and are

not

connected to the USB/Serial converter. That means you can use

them to connect to UART-devices like GPS's, fingerprint sensors, etc.

The TX pin is the output

from

the module. The RX pin is the input

into

the module. Both are 3.3V logic

I2C & SPI pins

You can use the ESP32 to control I2C and SPI devices, sensors, outputs, etc. If using with Arduino, the standard Wire

and SPI devices work as you'd expect!

The ESP32 runs on 3.3V power and logic, and unless otherwise specified, GPIO pins are not 5V safe!