Why did the Soviets invade Afghanistan?

Why did the Soviets invade Afghanistan? Is it because the Afghanistan muslims were sparking uprisings in the Soviet muslim countries? Also, has the Taliban been supplying the Chechens?
Also, is there a link between the Taliban and the Albanians?

Afghanistan is in a key position to be a buffer state between Russia and the lands to the south. Although Afghanistan is not oil-rich and has no seaports, it is directly adjacent to several countries that have both and that are separated from Russia only by Afghanistan.

Regardless which model you use (the U.S.S.R. wanted to conquer the world or the U.S.S.R. wanted to ensure that it shared no borders with a potentially hostile nation), having an independent Afghanistan was a sore in the side of the Kremlin (as it had been a sore in the side of the Czar, earlier). Through various machinations such as all the superpowers employ, the U.S.S.R. got a puppet government installed, but the Afghanis rebelled. The Soviets went in to “defend” their puppet government–just as we went in to “defend” the South Vietnamese government.

“Has the Taliban been supplying the Chechens?”
Yes, they enjoy good relations:

CBS News May 31, 2000

Pravda (translated) July 4, 2001

There were news reports of Afghan guerillas fighting in Bosnia, but the phenomenon was apparently pretty rare, and the few news reports about it went nowhere. I haven’t seen any reports about the Taliban working with the Albanians in Kosovo or Macedonia. The Albanian uprisings seem to come from an ethnic identity, rather than a religious one.