Terahertz spectroscopy is a technique used to study the interaction between matter and terahertz radiation, which falls in between the microwave and infrared regions of the electromagnetic spectrum. This technique is valuable for determining the structural and dynamic properties of materials such as polymers, semiconductors, biomolecules, and gases. Terahertz spectroscopy is particularly useful for studying low-energy excitations and vibrations in materials, as well as for identifying and characterizing new materials based on their unique terahertz absorption and reflection properties. This research area has applications in areas such as materials science, chemistry, physics, biology, and medicine.