  Effective Field Theory (EFT) stands as a cornerstone in modern theoretical
physics, offering a powerful framework for describing the dynamics of physical
systems across a wide range of energy scales. This article provides an in-depth
exploration of EFT and its diverse applications in various branches of physics.
Beginning with a foundational overview of EFT principles, including its
formulation, renormalization, and power counting rules, we delve into its
versatility in addressing complex phenomena beyond the reach of traditional
approaches. In particle physics, EFT techniques are indispensable for precision
calculations and theoretical predictions, enabling the systematic treatment of
quantum field theories at energies inaccessible to direct experimentation.
Moreover, EFT plays a crucial role in understanding the low-energy dynamics of
hadrons, nuclei, and other strongly interacting systems. This article aims to
provide a comprehensive introduction to EFT and as an example of constructing
EFT from a fundamental theory like QCD we explore how to construct a soft
collinear effective theory SCET.
