Quantum metrology explores quantum techniques that surpass classical methods in precision. Classical estimation theory limits precision as $ n^{-1/2} $, but quantum effects like entanglement can achieve $ n^{-1} $, known as the Heisenberg bound. This review discusses recent advancements in quantum metrology, focusing on quantum estimation theory, parameter estimation for channels, and the impact of noise and experimental imperfections. Quantum metrology involves three stages: probe preparation, interaction with the system, and readout. The standard quantum limit (SQL) is the classical limit, but quantum strategies can surpass it. The quantum Cramér-Rao (q-CR) bound provides a fundamental limit, achievable with local measurements and classical communication. For multi-parameter cases, the q-CR bound may not always apply, but it remains a useful benchmark. Quantum parameter estimation for channels involves optimizing probe preparation and interaction. The quantum Fisher information (QFI) plays a key role in determining the precision of parameter estimation. For unitary channels, the Heisenberg bound can be achieved with entangled states, while non-unitary channels are limited by the SQL. In quantum interferometry, the Mach-Zehnder interferometer is a key example. Using NOON states, which are superpositions of photon number states, can achieve the Heisenberg bound. However, noise and photon loss can degrade performance. Despite this, quantum strategies can still outperform classical methods, especially in controlled environments. Filtering protocols use classical states and post-selection to achieve super-resolution but cannot achieve super-sensitivity. Nonlinear estimation strategies can surpass the Heisenberg bound, but their practical implementation is challenging. Quantum metrology with noise is complex, as noise can significantly affect precision. However, optimized states and strategies can mitigate noise effects. For example, NOON states can be used in low-loss environments, while other strategies can achieve sub-shot-noise scaling. In conclusion, quantum metrology offers significant advantages over classical methods, particularly in precision and sensitivity. However, practical implementation is influenced by noise, resource constraints, and the choice of measurement strategies. Advances in quantum technologies continue to push the boundaries of what is possible in precision measurement.Quantum metrology explores quantum techniques that surpass classical methods in precision. Classical estimation theory limits precision as $ n^{-1/2} $, but quantum effects like entanglement can achieve $ n^{-1} $, known as the Heisenberg bound. This review discusses recent advancements in quantum metrology, focusing on quantum estimation theory, parameter estimation for channels, and the impact of noise and experimental imperfections. Quantum metrology involves three stages: probe preparation, interaction with the system, and readout. The standard quantum limit (SQL) is the classical limit, but quantum strategies can surpass it. The quantum Cramér-Rao (q-CR) bound provides a fundamental limit, achievable with local measurements and classical communication. For multi-parameter cases, the q-CR bound may not always apply, but it remains a useful benchmark. Quantum parameter estimation for channels involves optimizing probe preparation and interaction. The quantum Fisher information (QFI) plays a key role in determining the precision of parameter estimation. For unitary channels, the Heisenberg bound can be achieved with entangled states, while non-unitary channels are limited by the SQL. In quantum interferometry, the Mach-Zehnder interferometer is a key example. Using NOON states, which are superpositions of photon number states, can achieve the Heisenberg bound. However, noise and photon loss can degrade performance. Despite this, quantum strategies can still outperform classical methods, especially in controlled environments. Filtering protocols use classical states and post-selection to achieve super-resolution but cannot achieve super-sensitivity. Nonlinear estimation strategies can surpass the Heisenberg bound, but their practical implementation is challenging. Quantum metrology with noise is complex, as noise can significantly affect precision. However, optimized states and strategies can mitigate noise effects. For example, NOON states can be used in low-loss environments, while other strategies can achieve sub-shot-noise scaling. In conclusion, quantum metrology offers significant advantages over classical methods, particularly in precision and sensitivity. However, practical implementation is influenced by noise, resource constraints, and the choice of measurement strategies. Advances in quantum technologies continue to push the boundaries of what is possible in precision measurement.