In quantum information theory, one of the central goals is to understand how the information contained in physical systems can be represented, transformed, and transmitted under the laws of quantum mechanics. Unlike the classical framework, where states can be freely copied and distributed, quantum states obey fundamental constraints that completely alter our intuition about the duplication and processing of information. Among these limitations is the no-cloning theorem, which states that it is impossible to construct a unitary procedure that exactly reproduces an unknown quantum state without degrading or destroying it. Far from being a technical obstacle, this result constitutes a structural principle that defines the boundaries of physically realizable operations and shapes the behavior of quantum channels, cryptographic protocols, and communication tasks.