A tensor is a mathematical object that generalizes scalars, vectors, and matrices. It can be thought of as a multi-dimensional array of numbers that transforms according to specific rules when the coordinate system changes. Tensors are used in various fields, including physics, engineering, and computer science, to represent data and relationships in a structured way. In the context of machine learning and deep learning, tensors are essential for processing and storing data. They allow for efficient computation and manipulation of large datasets, making them fundamental in training models, such as neural networks. Tensors can have different ranks, indicating the number of dimensions they possess, which helps in organizing complex data.