user33613: What are the differences between the Arduino Micro and Pro Micro?

user19409: I actually think you are meaning what is the difference between the Arduino Mini and the Arduino Pro Mini, since there is no such board as the Arduino Pro Micro. However there is a board called the Arduino Micro and also the Sparkfun Pro Micro, so this answer will look at all four.
Arduino Mini
 
Arduino Pro Mini

Arduino Micro
 
(Sparkfun) Pro Micro
 
Microcontroller
Arduino Mini: ATmega328
Arduino Pro Mini: ATmega328 (ATmega168 on older boards)
Arduino Micro: ATmega32U4
Pro Micro: ATmega32U4  
Memory
All four have 32KB of Flash and 1KB of EEPROM
Both Minis have 2KB of SRAM where as both Micro boards have 2.5KB  
Digital I/O
Both Minis have 14 (of which 6 provide PWM output)
The Arduino Micro has 14 also (of which 7 provide PWM output)
Some of the analog pins can also be used as digital I/O
The Pro Micro has 12 (5 PWM pins)
Analog Inputs
Arduino Mini/Pro Mini: 8 (some boards only break out 6 analog inputs)
Arduino Micro: 12 (6 dedicated and 6 from digital I/O pins)
Pro Micro: 9 channels of 10-bit ADC
USB
Arduino Mini/Pro Mini: Requires FTDI cable or Sparkfun breakout board to provide USB power and communication to the board.
Arduino Micro / Pro Micro: Native USB  
Clock
All 16 MHz
(Some 3V3 variants run at 8MHz)
Power
Arduino Mini: 7-9 V
Arduino Pro Mini: There are two version of the Pro Mini. One runs at 3.3V and 8 MHz, the other at 5V and 16 MHz. VRAW  can accept voltage up to 12VDC.
Arduino Micro: USB or external supply of 6 to 20 volts (recommended range is 7 to 12 volts)
Pro Micro: can accept voltage up to 12VDC
Interrupts
Arduino Pro Mini: The Atmega328 has 2 hardware interrupts available
Arduino Micro / Pro Micro: The ATMega32u4 has 5 hardware interrupts available
credit: Enric Blanco 

33613: <p>What are the differences between the Arduino Micro and Pro Micro?</p>
 19409: <p>I actually think you are meaning what is the difference between the <a href="https://store.arduino.cc/arduino-mini-05" rel="noreferrer">Arduino Mini</a> and the <a href="https://store.arduino.cc/usa/arduino-pro-mini" rel="noreferrer">Arduino Pro Mini</a>, since there is no such board as the <em>Arduino Pro Micro</em>. However there is a board called the <a href="https://store.arduino.cc/usa/arduino-micro" rel="noreferrer">Arduino Micro</a> and also the <a href="https://www.sparkfun.com/products/12640" rel="noreferrer">Sparkfun Pro Micro</a>, so this answer will look at all four.</p>

<p><a href="https://store.arduino.cc/arduino-mini-05" rel="noreferrer">Arduino Mini</a><br>
<a href="https://i.stack.imgur.com/PLY8h.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/PLY8h.jpg" alt="Arduino Mini"></a>  </p>

<p><a href="https://store.arduino.cc/usa/arduino-pro-mini" rel="noreferrer">Arduino Pro Mini</a><br>
<a href="https://i.stack.imgur.com/LKcvq.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/LKcvq.jpg" alt="Arduino Pro Mini"></a></p>

<p><a href="https://store.arduino.cc/usa/arduino-micro" rel="noreferrer">Arduino Micro</a><br>
<a href="https://i.stack.imgur.com/l4hOF.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/l4hOF.jpg" alt="Arduino Micro"></a>  </p>

<p><a href="https://www.sparkfun.com/products/12640" rel="noreferrer">(Sparkfun) Pro Micro</a><br>
<a href="https://i.stack.imgur.com/pzZiL.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/pzZiL.jpg" alt="Pro Micro"></a>  </p>

<p><strong>Microcontroller</strong><br>
Arduino Mini: ATmega328<br>
Arduino Pro Mini: ATmega328 (ATmega168 on older boards)<br>
Arduino Micro: ATmega32U4<br>
Pro Micro: ATmega32U4  </p>

<p><strong>Memory</strong><br>
All four have 32KB of Flash and 1KB of EEPROM<br>
Both Minis have 2KB of SRAM where as both Micro boards have 2.5KB  </p>

<p><strong>Digital I/O</strong><br>
Both Minis have 14 (of which 6 provide PWM output)<br>
The Arduino Micro has 14 also (of which 7 provide PWM output)<br>
Some of the analog pins can also be used as digital I/O<br>
The Pro Micro has 12 (5 PWM pins)</p>

<p><strong>Analog Inputs</strong><br>
Arduino Mini/Pro Mini: 8 (some boards only break out 6 analog inputs)<br>
Arduino Micro: 12 (<a href="https://www.arduino.cc/en/uploads/Main/ArduinoMicro_Pinout3.png" rel="noreferrer">6 dedicated and 6 from digital I/O pins</a>)<br>
Pro Micro: 9 channels of 10-bit ADC</p>

<p><strong>USB</strong><br>
Arduino Mini/Pro Mini: Requires FTDI cable or Sparkfun breakout board to provide USB power and communication to the board.<br>
Arduino Micro / Pro Micro: Native USB  </p>

<p><strong>Clock</strong><br>
All 16 MHz<br>
(Some 3V3 variants run at 8MHz)</p>

<p><strong>Power</strong><br>
Arduino Mini: 7-9 V<br>
Arduino Pro Mini: There are two version of the Pro Mini. One runs at 3.3V and 8 MHz, the other at 5V and 16 MHz. VRAW  can accept voltage up to 12VDC.<br>
Arduino Micro: USB or external supply of 6 to 20 volts (recommended range is 7 to 12 volts)<br>
Pro Micro: can accept voltage up to 12VDC</p>

<p><strong>Interrupts</strong><br>
Arduino Pro Mini: The Atmega328 has 2 hardware interrupts available
Arduino Micro / Pro Micro: The ATMega32u4 has 5 hardware interrupts available<br>
credit: <a href="https://arduino.stackexchange.com/a/34577/19409">Enric Blanco</a> </p>
