What are the Arduino micro and Pro micro board?

Qwiic Pro Micro USB-C (ATmega32U4) - SparkFun

pro micro - Microcontrollers - Arduino Forum

New Pro Micro for arduino ATmega32U4 5V/16MHz Module with 2 row pin header For Leonardo in stock . best quality - AliExpress

Spice up your DIY keyboard builds with this little microcontroller, which works with the TMK and QMK firmware. It's got 18 pins for you to work with.

Pro Micro (Micro-USB) - 5V/16MHz - Arduino-compatible ATmega32U4

Arduino Pro Micro, ATMega32U4 Arduino Board

Arduino Micro Pro ATMEGA32U4 5V/16MHZ

Pro Micro ATmega32U4 Board 5V 16MHz Compatible with Arduino Pro Micro ATmega32U4

ATmega32U4 Pro Micro Controller Board for Arduino Pro Micro 5V TYPE-C – eElectronicParts

Products

Arduino Pro-Micro – PrismaKBD

The case of the broken Pro Micro (reprise) – gr33nonline

Pro Micro ATMEGA32U4 Arduino Pins and 5V, 3.3V Explained

Pro Micro & Fio V3 Hookup Guide - SparkFun Learn

Getting started with the Pro Micro Arduino Board

Arduino Micro — Arduino Official Store