Michaelis-Menten kinetics describes the rate of enzymatic reactions by relating reaction rate to substrate concentration. It is based on the formation of an enzyme-substrate complex, which then converts to product. The model is characterized by two key parameters: Vmax, the maximum reaction rate, and Km, the substrate concentration at which the reaction rate is half of Vmax. This model assumes that the formation of the enzyme-substrate complex is a rapid equilibrium, while the conversion to product is a slower step. It is widely used in biochemistry to understand how enzymes function and how they can be affected by various factors.