Sony’s A mount is the result of their purchase of Minolta’s camera division in 2006. Sony inherited most of Minolta’s innovative technology, including their autofocus lens mount, Minolta AF. Sony’s DSLRs used the A mount until the mirrorless E mount became the standard.
Sony A and Minolta AF are physically identical, and Minolta AF lenses can be used on Sony A bodies without issue. Sony also improved the lens mount over time, adding fast and quiet focusing motors (SSM) to lenses and improving coatings. Their collaboration with Carl Zeiss also added high quality lenses to the system.
As of now, Sony’s A mount is officially discontinued. The lenses can be used on E mount mirrorless cameras with the aid of an LA-EA3 or LA-EA4 adapter.