Steam
To cook food in the steam rising from boiling water, eg steam the vegetables for 5-10 minutes or until cooked.
Steamer
A device which produces steam to cook food. Steamed foods are cooked by a gentle, moist heat. There is a wide choice of steamers available from electric to hob-top models which consist of a base pan topped with two or three inserts that fit together and are topped with a close fitting lid.