Info that the user of a class needs to know should go into a Javadoc comment.
Info that a developer modifying a class needs to know go into a normal comment (block or line).
And it’s very possible that any block of code (class, interface, field, method, constructor, …) can have both a Javadoc comment and a normal comment block, when both publicly visible as well as internal documentaton is required.
Personally I tend towards writing very little non-Javadoc comments, because I prefer to structure my code in a way that it’s self-documenting.