Gas hydrates consist of guest gas molecules inside hydrogen-bonded water lattices. Natural gas hydrates are found in offshore and permafrost regions. The large amounts of gas hydrate reserves suggest the potential of gas hydrates as an energy resource if economically viable production methods were developed. The proper understandings of hydrate formation/dissociation are important for the drilling and oil production applications. The investigations of physical and geotechnical properties provide the in-depth understandings of the in-situ hydrate formation mechanism and the associated production technologies. The purpose of this review paper is to provide a starting kit for civil engineers who have recently started the research related to the hydrate development and production and want to have insights on the general trends of the hydrate research and the relevant knowledge needed for their research. Gas hydrate explorations include the geophysical explorations, such as the seismic survey, the borehole logging and the geological and geochemical explorations. Gas hydrate productions require the dissociation of gas hydrates, and the production technologies are categorized based on the dissociation techniques involved: depressurization method, thermal stimulation method, and inhibitor injection method. Establishing safe and efficient gas production technology requires the extensive information on the geotechnical characteristics of hydrate reservoirs. Flow assurances, the integrity of sediment formation and the well bore stability are crucial for the safe and efficient productions of gases from gas hydrates in sediments. The strength and deformation characteristics, the fluid migration characteristics, and the thermal conduction characteristics are key factors for controlling the above.