What are the Arduino micro and Pro micro board?

Arduino Pro Micro

【ATmega32U4 microcontroller】-The Pro Micro is similar to the Pro Mini except with an ATmega32U4 on board. The USB transceiver inside the 32U4 allows

3PCS Pro Micro ATmega32U4 5V/16MHz Module Board 2 Row Pin Header for Arduino Mini Leonardo

Arduino Pro Micro Installation

Type-C MINI USB Pro Micro For Arduino ATmega32U4 5V/16MHz 3.3V/8Mhz Module With 2 Row Pin Header Leonardo Usb Interface Board - AliExpress

Arduino Pro Micro – FirstMotionLab

Arduino Micro — Arduino Official Store

Description Cytron Arduino Pro Micro Compatible w/ Pre-soldered Headers Comes with pre-soldered header pins Provides Rx and Tx Hardware Serial

Cytron Arduino Pro Micro Compatible w/ Pre-soldered Headers

Sparkfun Pro Micro: Arduino IDE Compatible Board Overview

SparkFun 12640 Pro Micro - 5V/16MHz