A tesseract is a four-dimensional geometric shape, also known as a hypercube. While we live in a three-dimensional world, a tesseract extends the concept of a cube into an additional dimension. Just as a cube has six square faces, a tesseract has eight cubic cells. In mathematics and physics, tesseracts are used to help visualize and understand higher dimensions. They can be represented in three dimensions through projections, similar to how a cube can be drawn on a flat surface. Tesseracts are often discussed in the context of theoretical physics and science fiction, where they may represent concepts like time travel or alternate realities.