Short answers, pulled from the story.
The formal beginning of Operation Storm-333 occurred on the 25th of December 1979 when Defence Minister Dmitry Ustinov issued an order for ground and air forces to cross state frontiers. The operation concluded by morning on the 28th of December 1979 after Soviet troops occupied major governmental buildings including Tajbeg Palace.
By 1985, the Limited Contingent of Soviet Forces reached 108,800 personnel which marked the bloodiest year of the war. The initial Soviet force numbered around 1,800 tanks and 80,000 soldiers before later divisions brought total personnel above 100,000.
Estimates indicate that one to three million Afghans died between 1980 and 1985 due to the conflict. Between 6.5% and 11.5% of Afghanistan's population of 13.5 million people per the 1979 census died during the war.
The last Soviet military column crossing into Uzbek SSR occurred on the 15th of February 1989 marking the end of direct Soviet involvement. An official announcement declaring withdrawal of Soviet troops from the country had been made earlier on the 20th of July 1987.
Osama bin Laden led an Arab group that eventually evolved into al-Qaeda after joining thousands of volunteer fighters known as Afghan Arabs. Only about 2,000 fought at any one time compared to 250,000 Afghan fighters while Pakistan's North-West Frontier Province served as the primary base for resistance operations.