A CW complex is a type of topological space used in algebraic topology. It is constructed by gluing together basic building blocks called cells, which are homeomorphic to disks of various dimensions. The construction starts with 0-dimensional cells (points), then adds 1-dimensional cells (lines), followed by 2-dimensional cells (disks), and so on. This process allows for a flexible way to create complex shapes while maintaining a clear structure. The name CW comes from the terms "closure-finite" and "weak" topology. A CW complex is characterized by having a finite number of cells in each dimension, ensuring that it is manageable for mathematical analysis. This structure is essential for studying properties like homotopy and homology, which are fundamental concepts in the field of algebraic topology.