Why use 'way' in this sentence?

Question

This question is way too vague

Why not just: "This question is too vague"? What's the meaning of 'way' in this sentence?

Answer 1

In American English, way is also used informally as an adverb of emphasis. Relevant definitions, according to the Oxford Dictionaries:

at or to a considerable distance or extent; far (used before an adverb or preposition for emphasis): his understanding of what constitutes good writing is way off target
my grandchildren are way ahead of others their age

• [as submodifier] much:
  I was cycling way too fast

• [usually as submodifier] extremely; really (used for emphasis):
  the guys behind the bar were way cool

Thus, in your example, way is used to emphasize the vagueness of the question. You could just as well say:

This question is far too vague.

Answer 2

Way is acting as an intensifier. Saying that something is way too vague indicates that is more vague than if you had simply said it is too vague.

In this context it is an informal synonym for much, i.e. "This question is much too vague."