Consultative means you give advice and suggest ways to solve a problem, but you do not give the final order. A consultative committee listens, talks, and recommends; someone else still decides. It is a fairly formal word, at home in government, offices, and official notices: a consultative role, a consultative process, a consultative body. It does not mean “related to a consul.” It comes from consult — to ask for advice — and that is the whole of it. In everyday talk people more often say advisory, or just “they only advise; they don’t decide.”