Short answers, pulled from the story.
The Sino-Vietnamese War began on the 17th of February 1979 when People's Liberation Army forces entered northern Vietnam. China withdrew its troops on the 16th of March 1979 after approximately one month of conflict.
Xu Shiyou commanded the eastern direction while Yang Dezhi led the western direction of the invasion. The operation involved about 200,000 PLA troops entering Vietnamese territory in early 1979.
China launched the attack because Vietnam signed a formal military alliance with the Soviet Union on the 3rd of November 1978. Deng Xiaoping viewed this development as threatening China's southern border security following deteriorating relations between the Soviet Union and China since 1953.
Fighting occurred mainly in the provinces of Cao Bằng, Lào Cai, and Lạng Sơn. Chinese forces advanced about 15 to 20 kilometers into Vietnamese territory before capturing cities like Lạng Sơn which fell on the 6th of March 1979.
Chinese military sources indicate China suffered 6,954 dead while Deputy chief Wu Xiuquan revealed Vietnam suffered 50,000 casualties. The Vietnamese state newspaper Nhân Dân claimed Vietnam suffered more than 10,000 civilian deaths during the invasion.