Explore the fundamentals of quantum sensor networks in this comprehensive lecture, the first in a series on Precision Measurements and Quantum Metrology. Delve into the emerging field of quantum technologies as Professor Saikat Guha introduces key concepts and applications. Learn how quantum physics principles are being harnessed to develop advanced sensors, encryption tools, and computing systems with unprecedented accuracy. Discover the importance of quantum resources such as entanglement, superposition, and coherence in pushing the boundaries of measurement precision. Gain insights into the theory of precision measurements, estimation techniques, and the intersection of classical and quantum metrology. This lecture sets the foundation for understanding the cutting-edge research and potential applications in quantum sensing, preparing students and researchers for the future of quantum technology and its role in India's National Quantum Mission.