Why is benzyne an intermediate?
Intermediate is a middle step in the chemical process: reactants -> intermediate(s) -> products. Benzyne is formed from benzene and is highly reactive. Thus, it is never the first or last step of the process. To my knowledge benzyne is rarely observed as a product, because its reacting fast with other molecules because its triple bond.

What makes a molecule an intermediate? It is a highly reactive "middle product" of a reaction.
See here and there.