Question about Eclipse and JDK

Hello,

My quesiton is somewhat basic.
Today I downloaded Eclipse on my new laptop. Laptop already has JRE 1.6 on it. My quesiton is, do I need JDK to work with eclipse my java programs/applications. Basically I am still struglling little bit to understand difference between JDK and JRE. When I downloaded NetBeans while back, I was told on download site that I need JDK for getting NetBeans working. Do I need JDK for for Eclipse.
I know JDK is development kit annd comes with utilities, tools, libraries for developing java. But where exactly it stands with Eclipse. Do I get it default when I downloaded eclipse?
I ran wrote, complied and run one sample java program in Eclipse without having JDK on my machine. It all went fine. So does it mean it comes with it?

Can you please help me to understand this.

Thanks in advance

Prasad

Eclipse has its own, built-in Java compiler. It does not need the JDK to compile Java programs. Eclipse has originally been developed by IBM and has a built-in compiler based on IBM's Jikes Java compiler.