Seismic inversion methods attempt to find an earth model that fits the seismic data. It is a way of transforming the seismic data to rock and/or reservoir properties. It can be simply summarized as the creation of the pseudo well logs from seismic data. Most of the methods and techniques discussed are universal and often barrowed from the inverse problem solutions employed in the other fields known as system identification. Sonic log and acoustic impedance (AI) sections obtained from stacked seismic data in 1970s was a major step because the transformations from seismic trace looked like geological layering with quantitative information. This attracted the attention of all geoscientists other than geophysicists, and improved communication among workers and researchers in the world of hydrocarbon exploration and development. Since eighties the rock properties extractions from seismic data are related to reservoir properties, or the reservoir properties are directly estimated or extracted from seismic data.