The article provides a comprehensive overview of quantum entanglement, its fundamental concepts, and its applications. Entanglement, recognized by Einstein, Podolsky, Rosen, and Schrödinger, is a nonclassical property of composite quantum systems where subsystems are correlated in ways that cannot be described by classical physics. The authors discuss various manifestations of entanglement, including Bell inequalities, entropic inequalities, entanglement witnesses, and their roles in quantum cryptography, teleportation, and dense coding. They also explore the challenges of detecting and quantifying entanglement, the irreversibility of entanglement manipulations, and the role of entanglement in quantum communication and quantum computing. The article highlights the importance of entanglement in quantum information processing and the development of quantum technologies, emphasizing the need for robust and efficient methods to detect and manipulate entanglement.The article provides a comprehensive overview of quantum entanglement, its fundamental concepts, and its applications. Entanglement, recognized by Einstein, Podolsky, Rosen, and Schrödinger, is a nonclassical property of composite quantum systems where subsystems are correlated in ways that cannot be described by classical physics. The authors discuss various manifestations of entanglement, including Bell inequalities, entropic inequalities, entanglement witnesses, and their roles in quantum cryptography, teleportation, and dense coding. They also explore the challenges of detecting and quantifying entanglement, the irreversibility of entanglement manipulations, and the role of entanglement in quantum communication and quantum computing. The article highlights the importance of entanglement in quantum information processing and the development of quantum technologies, emphasizing the need for robust and efficient methods to detect and manipulate entanglement.