The technology is ubiquitous today due to its inclusion as standard equipment in nearly all new cars and trucks, but it remained optional in a number of lower-priced, entry-level cars throughout the 1980s and 1990s.
The purpose of power steering is to reduce the amount of effort that it takes for the driver to steer. This was traditionally accomplished through hydraulic power, which can be generated by a belt-driven pump that runs off the rotation of the engine. However, the technology has undergone a steady stream of innovations and upgrades since it first showed up as an OEM option in the 1950s.
The first major upgrade to traditional hydraulic power steering that saw any sort of wide uptake was electro-hydraulic power steering. This early form of electric power steering added additional assistance to traditional power steering with electric pumps.