Coherent states are specific quantum states of a harmonic oscillator that closely resemble classical states. They are characterized by having minimum uncertainty, meaning that the uncertainties in position and momentum are balanced according to the Heisenberg uncertainty principle. These states are often used in quantum optics to describe the behavior of laser light. In mathematical terms, coherent states can be represented as eigenstates of the annihilation operator in quantum mechanics. They play a crucial role in various fields, including quantum information, quantum computing, and quantum field theory, as they provide insights into the transition between classical and quantum systems.