Short answers, pulled from the story.
The Soviet-Afghan War lasted from December 1979 to February 1989, a period of approximately nine years. The last Soviet military column crossed into the Uzbek SSR on the 15th of February 1989, ending direct Soviet military involvement.
Between one and three million Afghans died during the Soviet-Afghan War. Based on the 1979 census population of 13.5 million, between 6.5 and 11.5 percent of Afghanistan's entire population is estimated to have been killed.
Operation Cyclone was the CIA program that channelled support to anti-Soviet mujahideen forces through Pakistani intelligence services. Combined US, Saudi, and Chinese aid to the mujahideen totaled between six and twelve billion dollars over the course of the war.
The Soviet leadership, led by a troika of KGB chairman Yuri Andropov, Foreign Minister Andrei Gromyko, and Defense Minister Dmitry Ustinov, decided to remove the erratic Afghan leader Hafizullah Amin and replace him with moderate communist Babrak Karmal. They feared a radical Islamist regime in Kabul would sponsor Islamic unrest in Soviet Central Asian republics, and believed the occupation would be short and relatively painless.
Osama bin Laden was a young Saudi who joined the foreign volunteer fighters known as Afghan Arabs, who wished to wage jihad against the Soviet-backed Afghan government. His Arab group eventually evolved into al-Qaeda. The contribution of these foreign fighters to the actual fighting was described as a 'curious sideshow,' with only an estimated 2,000 fighting at any one time.
The decade-long war inflicted mounting military, economic, and political costs on the Soviet Union as resources became increasingly exhausted. Scholars have cited it as a significant contributing factor to the dissolution of the Soviet Union in December 1991, and the conflict is sometimes called 'the Soviet Union's Vietnam.'