Mujahideen and Taliban are two terms that can't be used to describe two different groups. The mujahideens that US trained back then, are now fighting under Taliban. Taliban is a group of mujahideens. So you basically created the army that call themselves Taliban.
let me make it clear for you -
1. Taliban was created by Mullah Omar in mid 90's to take over Afghanistan because after war against USSR, America & allied nations left them.. didn't care about them. Afghanistan, a war-torn country, plunged into years-long of tribal wars and poverty. Afghans supported Taliban's original view and thought it would bring stability to country - the strictest interpretation of Sharia law. Later - Taliban got corrupted and abusive. Now the Afghans do not want Taliban to come back.
2. Al Qaeda was created by Osama bin Laden and Abdullah Azzam in around 1988. Its mission was to wage a jihad against those who attack Arab nations
3. Both are Sunni Islamist fundamentalists
4. Taliban is consisted of Pashtun tribes in Afghanistan
5. Al Queda is consisted of mujahideen from several Arab nations
6. The mujahideen that we trained & funded to fight against USSR in Afghanistan... they were from all Arab countries as volunteers. After the war - many returned to their home countries. The remaining few hundreds (or thousands) stuck around to stay with Osama bin Laden.
7. Saudi Arabia government exiled Osama bin Laden and Taliban offered him to come in
8. since Osama bin Laden and Mullah Omar shared same agendas - they became allies but Mullah Omar wasn't too pleased about Osama bin Laden coming in and taking control but hey - what can he do about it? Osama bin Laden has what Mullah Omar doesn't have - thousands of well-seasoned, highly-trained soldiers, global connections, and money. lots lots lots of money.