It's a term you may not hear often.
Quines are computer programs whose output is the source code of the program itself! Don't get it?
You can also call them as "self-reproducing" or "self-documenting" programs.
Here's an example in Java.
class S{
public static void main(String[]a){
String s="class S{public static void main(String[]a){
String s=;char c=34;System.out.println(
s.substring(0,52)+c+s+c+s.substring(52));}}";
char c=34;
System.out.println(s.substring(0,52)+c+s+c+s.substring(52));
}
}
Now, what happens when you run this program? It prints -
class S{
public static void main(String[]a){
String s="class S{public static void main(String[]a){
String s=;char c=34;System.out.println(
s.substring(0,52)+c+s+c+s.substring(52));}}";
char c=34;
System.out.println(s.substring(0,52)+c+s+c+s.substring(52));
}
}
The program itself! Interesting, isnt it?
If this tickles your imagination, here's a list of quines in all languages you might have heard of: List of Quines.
Well, while you are at it, don't forget to read about iterating quines!