I am relatively new to Java Programming and I came across this declaration of an interface and a class that implements it:

```
public interface Abcd<E extends Comparable<E>>{
......
......
......
}

public class AbcdImpl<E extends Comparable<E>> implements Abcd<E>{
......
......
......
}

```

Can you explain what `<E extends Comparable<E>>` stands for and typically what does `<E>` signify?