The phrase "to grease the pan" means to apply a thin layer of oil or fat on the inside surface of a cooking pan to prevent food from sticking to it. Full definition
Line a standard cupcake pan with twelve paper baking cups, or grease the pan with butter if not using baking cups. (epicurious.com)
Fold cranberries into batter until mixed, place batter into grease pan. (savynaturalista.com)
I like to use mine to grease the pan before cooking, season roasted vegetables, make quick and easy garlic bread, and as a simple sauce for rice or pasta. (wellnesting.com)