Winter squash refers to a group of squash varieties that are harvested in the fall and have a hard outer shell. Common types include butternut, acorn, and spaghetti squash. Unlike summer squash, winter squash can be stored for several months due to their tough skin, making them a popular choice for winter cooking. These squashes are rich in nutrients, including vitamins A and C, fiber, and antioxidants. They can be roasted, pureed, or used in soups and stews. Their sweet, nutty flavor makes them a versatile ingredient in both savory and sweet dishes.