The article provides an introduction to the field of quantum sensing, which involves using quantum systems to measure physical quantities with high sensitivity and precision. Quantum sensors can be based on various platforms such as spin qubits, trapped ions, and flux qubits. The review covers the basic principles, methods, and concepts of quantum sensing, including the definition of quantum sensing, examples of quantum sensors, and the quantum sensing protocol. It discusses the sensitivity of quantum sensors, the role of noise, and the importance of decoherence. The article also explores advanced techniques such as adaptive methods, entanglement-enhanced sensing, and quantum error correction. Finally, it highlights the potential future developments in the field.The article provides an introduction to the field of quantum sensing, which involves using quantum systems to measure physical quantities with high sensitivity and precision. Quantum sensors can be based on various platforms such as spin qubits, trapped ions, and flux qubits. The review covers the basic principles, methods, and concepts of quantum sensing, including the definition of quantum sensing, examples of quantum sensors, and the quantum sensing protocol. It discusses the sensitivity of quantum sensors, the role of noise, and the importance of decoherence. The article also explores advanced techniques such as adaptive methods, entanglement-enhanced sensing, and quantum error correction. Finally, it highlights the potential future developments in the field.