It is important because it is the longest war in the world.
Well, this is kind of difficult to answer, but it has to do with the situation in Afghanistan before the war. I strongly recommend to you that you google 'soviet invasion of afghanistan' and click on the fourth result. It is a GREAT source; I just used nearly all of its information as a springboard for an essay this week. :)
operation enduring freedom
As the Taliban are not easy to eliminate, coupled with inefficient Afghan government / Internal Security Force which is akin to US puppet followed by some of the citizens are uneducated such that they supports Taliban, the whole operation is a failure, despite they have successfully removed Taliban government.
Well, Taliban right now uses guerrilla warfare, such kind of hit and run warfare was also used in China's civil war, Vietnam war & Korean war by the communist and they have the victory instead.
Operation Storm-333 («Шторм-333») was the codename of the Soviet special forces operation on December 27, 1979 in which Soviet special forces stormed the Tajbeg Palace in Afghanistan and killed President Hafizullah Amin and his 200 personal guards. His eleven year old son died due to shrapnel wounds.[1]
Several other government buildings were seized during the operation, including the Ministry of Interior building, the Internal Security (KHAD) building, and the General Staff building (Darul Aman Palace). Alpha Group's veterans call this operation one of the most successful in the group's history