Open Source is not a programing language. Here Source means program code and logic. Now open word indicates that there is no resctriction to modify or add or copy the code in order to achive new functionality but some terms, agreement and coditions must be there implemented by original coder/coders. So examples of open source products( i.e anything can be open source whether it is a operating system or programing language or database or any other type of software as far as coding (i.e source) is available to end user by which he can add, modify new features to it.) .
Eg:
Open Source OS - Linux
If you are a programmer you can add new functionality to the Linux OS or even you can create new Linux OS in your name
Opne Source Scripting Langauges are C, C++, Java for Linux , PHP Scripting, MySQL Database etc
On the other hand you cannot get the code or program source of Windows Operating System or MS Office etc to add or modify them c hence they are not open source .
You can get more detailed explanation at
http://www.opensource.org/