The quotes tell the compiler that you want to output the literal string as-is. The penultimate line of code is ordering main to return 0. When one returns a value to main, it is passed on to the operating system. It is accepted practice to some to declare main as a void, but to others it is extremely upsetting. After, the brace closes off the function.
Comments are extremely important to understand.
Certain compilers will change the color of a commented area, but some will not. Be certain not to accidentally declare part of your code a comment. So far you should be able to write a simple program to display information typed in by you, the programmer. However, it is also possible for your program to accept input. In programming, these locations where input and other forms of data are stored, are called variables.