What is worth knowing?

Near the beginning of the Apology, Socrates say (21d ):

I am wiser than this man; it is likely that neither of us knows anything worthwhile, but he thinks he knows something when he does not, whereas when I do not know, neither do I think I know; so I am likely to be wiser than he to this small extent, that I do not think I know what I do not know.

• What type of knowledge would Socrates consider "worthwhile"?
• If Socrates does not know anything worthwhile, in what way could he be more wise than others?