A hypersphere is a generalization of a sphere to higher dimensions. While a regular sphere exists in three-dimensional space, a hypersphere can exist in four or more dimensions. For example, a 2D hypersphere is a circle, a 3D hypersphere is a standard sphere, and a 4D hypersphere is often referred to as a 4-sphere. The concept of hyperspheres is important in various fields, including mathematics, physics, and computer science. They help in understanding complex shapes and spaces, particularly in theories involving higher dimensions, such as string theory and data analysis in machine learning.