Added playground definition

Added a small definition about programming/coding playgrounds for making it understandable to beginners

Author: Suman373

README.md

@@ -182,6 +182,8 @@ Free Podcasts and Screencasts:
 
 ### Programming Playgrounds
 
+Whether you're a beginner programmer or an expert developer, code/programming playgrounds are useful when sharing and learning with others. A programming playground is an online service where you can write, compile(or run), and share code with others. They also allows you to fork and get your hands dirty by playing around with other's code.
+
 + [Chinese / 中文](more/free-programming-playgrounds-zh.md)
 + [English](more/free-programming-playgrounds.md)