The paper discusses the distinction between "free" and "bound" entanglement in quantum systems. It shows that if a mixed state can be distilled into a singlet state, it must violate the partial transposition criterion. This implies that there are two types of entanglement: "free" entanglement, which can be distilled into a singlet state useful for quantum communication, and "bound" entanglement, which cannot be distilled and is thus not useful for quantum information tasks. The authors demonstrate that there exist inseparable states that do not violate the partial transposition criterion and therefore cannot be distilled. These states are considered "bound" entanglement, analogous to bound energy in thermodynamics. The paper also discusses the physical implications of these results, suggesting that entanglement can be viewed as a resource similar to energy, with "free" entanglement being usable for quantum communication and "bound" entanglement being non-usable. The results highlight the importance of the partial transposition criterion in determining distillability and suggest a connection between distillation, partial transposition, and time reversal. The paper concludes that not all inseparable states are nonlocal, and that the question of whether inseparable states with positive partial transposition are nonlocal remains open.The paper discusses the distinction between "free" and "bound" entanglement in quantum systems. It shows that if a mixed state can be distilled into a singlet state, it must violate the partial transposition criterion. This implies that there are two types of entanglement: "free" entanglement, which can be distilled into a singlet state useful for quantum communication, and "bound" entanglement, which cannot be distilled and is thus not useful for quantum information tasks. The authors demonstrate that there exist inseparable states that do not violate the partial transposition criterion and therefore cannot be distilled. These states are considered "bound" entanglement, analogous to bound energy in thermodynamics. The paper also discusses the physical implications of these results, suggesting that entanglement can be viewed as a resource similar to energy, with "free" entanglement being usable for quantum communication and "bound" entanglement being non-usable. The results highlight the importance of the partial transposition criterion in determining distillability and suggest a connection between distillation, partial transposition, and time reversal. The paper concludes that not all inseparable states are nonlocal, and that the question of whether inseparable states with positive partial transposition are nonlocal remains open.