Arduino
1. What is Arduino ?
Arduino is an open-source electronics platform based on easy-to-use hardware and software.
2. How many types of Arduino that we use ?
1. Arduino Mega ( Largest version of arduino )
2. Arduino Uno ( Smaller Than Arduino Mega )
3. Arduino Nano ( Smaller Than Arduino Uno )
4. Arduino Pro-Mini ( Smaller Than Arduino Nano )
3. What is Arduino Mega ?

The Arduino Mega 2560 is a microcontroller board based on the ATmega2560 . It has 54 digital input/output pins (of which 15 can be used as PWM outputs) , 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button .
4. What is Arduino Uno ?

The Arduino Uno R3 is a microcontroller ( ATmega328 AVR microcontroller ) board based on a removable. It has 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 can be used as analog inputs). Programs can be loaded on to it from the easy-to-use Arduino computer program. The Arduino has an extensive support community, which makes it a very easy way to get started working with embedded electronics. The R3 is the third, and latest, revision of the Arduino Uno.
5. What is Arduino Nano ?

Arduino Nano is one type of microcontroller board, and it is designed by Arduino.cc. It can be built with a microcontroller like Atmega328. It is a small size board and also flexible with a wide variety of applications.
6. What is Arduino Pro-mini ?

The Arduino Pro Mini is a microcontroller board based on the ATmega328.
It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, an on-board resonator, a reset button, and holes for mounting pin headers. A six pin header can be connected to an FTDI cable or Sparkfun breakout board to provide USB power and communication to the board.