Question

do they by annotation mean a comment in a code with // or /* */?

Answer 1

No, an annotation is not a comment. An annotation is added to a field, class or method, using the syntax @Annotation. One of the best known annotations is @Override, used to signal a method is overriding one from a super class. For example:

public class MyClass {
  @Override
  public boolean equals(Object other) {
    //...
  }
}

See http://download.oracle.com/javase/1,5.0/docs/guide/language/annotations.html for more info.