A tensor is a mathematical object that generalizes the concepts of scalars, vectors, and matrices. It can be thought of as a multi-dimensional array of numbers that can represent various physical quantities, such as stress, strain, or electromagnetic fields. Tensors are essential in fields like physics, engineering, and computer science, especially in machine learning and deep learning. Tensors have different ranks, which indicate their dimensions. A scalar is a rank-0 tensor, a vector is a rank-1 tensor, and a matrix is a rank-2 tensor. Higher-rank tensors can represent more complex relationships and are crucial for understanding phenomena in relativity and continuum mechanics.