What is Arduino
Arduino is an open-source electronics platform based on easy-to-use hardware and software. Arduino boards are able to read inputs – light on a sensor, a finger on a button, or a Twitter message – and turn it into an output – activating a motor, turning on an LED, publishing something online. You can tell your board what to do by sending a set of instructions to the microcontroller on the board. To do so you use the Arduino programming language (based on Wiring), and the Arduino Software (IDE) , based on Processing.
Click the link below to get more info.
https://www.arduino.cc/en/Guide/Introduction
The Arduino Platform
Arduino is composed of two major parts:
The Arduino board, which is the piece of hardware you work on when you build your objects. Arduino senses the environment by receiving inputs from many sensors, and affects its surroundings by controlling lights, motors, and other actuators.
The Arduino IDE, the piece of software you run on your computer. You use the IDE to create a sketch (a little computer program) that you upload to the Arduino board. The sketch tells the board what to do. You can tell your Arduino what to do by writing code in the Arduino programming language and using the Arduino development environment.