g++ - Does it matter which file extension I use for my C++ programs?

I am using Orwell Dev C++ 5.8.3 IDE. It uses g++ 4.8.1 compiler. When I am saving my C++ program files it shows to several file extensions for saving my C++ program files like .cpp, .cc, .cxx, .c++, .cp.

Does it matter which extension I choose?

Are these extensions compiler/IDE specific or platform specific?

I am using windows 7 operating system.

Are these extensions also available and / or valid to use on other operating systems like Unix or Linux?

Why there are so many extensions provided?

What is the reason?