POOLISH: A French term with Polish origins that is used to mean a preferment that is made with equal amounts of flour and water (which produces a pancake-like batter with a hydration of 100%), and a small amount of commercial yeast, but no salt. It is usually left to ferment and ripen at room temperature for several hours, although it is sometimes refrigerated for many hours (e.g., overnight) before incorporating into the final dough. The term poolish is pronounced poo-leash.
PREFERMENT: A partial preparation of flour and water and yeast (naturally-occurring or commercial), that may or may not include salt, that is left to ferment and mature before incorporating into the final dough. The ingredients and period of fermentation are controlled to achieve the desired leavening power and maturation (ripening) before incorporation into the final dough. The preferment can be fermented at room temperature or under refrigeration, or a combination of both. Depending on its final intended use, it can take a liquid form, semi-liquid form (like a batter) or it can be stiff and dough-like. The benefits from using a preferment include a strengthened gluten structure, a shortened overall production time, and superior crust flavor.
According to the glossary, PREFERMENT = STARTER