Calabi-Yau manifolds are complex, multi-dimensional shapes that play a crucial role in theoretical physics, particularly in string theory. They are characterized by their ability to preserve certain symmetries and have a rich geometric structure, which allows for the compactification of extra dimensions beyond the familiar three of space. These manifolds are named after mathematicians Eugenio Calabi and Shing-Tung Yau, who contributed significantly to their study. In string theory, Calabi-Yau manifolds provide a way to unify the fundamental forces of nature by allowing additional dimensions to be hidden or compactified, making them essential for understanding the universe's underlying framework.