user11429: Actually I don't know about Arduino, but seeing my fellow classmates, I want to start learning it. Could anybody tell what actually Arduino is about?

user10794: 
What is Arduino?
Arduino video tutorials
Official boards
Wikipedia - Arduino
Arduino forum


A popular Arduino - The Arduino Uno:


In case I get accused of writing a "link-only" answer ...
The Arduino is a hobbyist prototyping platform, where users can develop projects for microprocessors. Typically the boards have one or two processors on them, can connect to a PC/Mac/Linux by a USB interface, be programmed in C++, and operate external devices (eg. motors, lights, MIDI, LCD screens, LEDs) and take readings (eg. temperature, time, location, voltage).
Different boards have different capabilities, such as the number of I/O ports, the amount of memory, and the size of the program that can be uploaded.
You can connect them to the major operating systems:

Linux
Macintosh
Windows

The hardware and software are open-source, making development for them easy.

Image attribution: Sparkfun Electronics

11429: <p>Actually I don't know about Arduino, but seeing my fellow classmates, I want to start learning it. Could anybody tell what actually Arduino is about?</p>
 10794: <ul>
<li><a href="https://www.arduino.cc/" rel="nofollow noreferrer">What is Arduino?</a></li>
<li><a href="https://www.youtube.com/playlist?list=PLT6rF_I5kknPf2qlVFlvH47qHvqvzkknd" rel="nofollow noreferrer">Arduino video tutorials</a></li>
<li><a href="https://www.arduino.cc/en/Main/Products" rel="nofollow noreferrer">Official boards</a></li>
<li><a href="https://en.wikipedia.org/wiki/Arduino" rel="nofollow noreferrer">Wikipedia - Arduino</a></li>
<li><a href="http://forum.arduino.cc/" rel="nofollow noreferrer">Arduino forum</a></li>
</ul>

<hr>

<p>A popular Arduino - The Arduino Uno:</p>

<p><a href="https://i.stack.imgur.com/ovHc1.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ovHc1.jpg" alt="Arduino Uno"></a></p>

<hr>

<p>In case I get accused of writing a "link-only" answer ...</p>

<p>The Arduino is a hobbyist prototyping platform, where users can develop projects for microprocessors. Typically the boards have one or two processors on them, can connect to a PC/Mac/Linux by a USB interface, be programmed in C++, and operate external devices (eg. motors, lights, MIDI, LCD screens, LEDs) and take readings (eg. temperature, time, location, voltage).</p>

<p>Different boards have different capabilities, such as the number of I/O ports, the amount of memory, and the size of the program that can be uploaded.</p>

<p>You can connect them to the major operating systems:</p>

<ul>
<li>Linux</li>
<li>Macintosh</li>
<li>Windows</li>
</ul>

<p>The hardware and software are open-source, making development for them easy.</p>

<hr>

<p>Image attribution: <a href="http://www.flickr.com/people/41898857@N04" rel="nofollow noreferrer">Sparkfun Electronics</a></p>
