Answer: dreams and ambition by using metaphors.
Explanation: As you know, a metaphor is acomparison between things that are not related with each other at first sight, that is why that In the given excerpt from Act II of "Hamlet" by William Shakespeare, we can see the use of metaphors to compare and describe dreams (by comparing them to ambition and shadow: "Which dreams, indeed, are ambition" and "A dream itself is but a shadow") and ambition (by comparing it to a shadow's that can be: "and I hold ambition of so airy and light a quality that it is but a shadow’s shadow". Hope this helps.