Close your eyes, imagine going back in your ancestry thousands and thousands of years.
It doesn't matter which ancestry you come from any ancestry thousands and thousands of years ago would be similiar.  Go back 40 to 100 thousand years.  What you will find is small groups of people living in tribes and vilages.  Some were nomadic, some not.  These ancients were dependant on nature and had to know the ways that nature worked for survival.  They lived in tune with the seasons, the weather, the growing patterns and the migration of animals, birds and fish.  They spoke to the spirits of weather to bring rain, and they spoke with the spirits of the animals they killed for food, thanking them for the sacrifice of their lives for the survival of the people in the tribes and villages.  They spoke with the plants to find out which plant healed which ailment, or where which plant grew best for food.  They knew the ways in the spirit world and could ask for spirit helpers to heal each other from illness.

Illness was looked at as not only physical disease, but bad luck, poor hunting, disharmony among a familiy or village.  And these ancients knew that all that manifests physically began in the spirit world, so had to be dealt with in the spirit world first.

Now, come back to modern times.  We may no longer be indigenious people, but we still need our tribes and villages.  In fact much of our emotional illnesses today stem from this illusion that we are separate from nature and from each other.  Shamanism is based on this connection in the spirit world with nature and each other.  And it is just as important today, if not more important, than it ever has been. 

We in modern western civilization are so materially focused that we have forgotten the spirit beings who walk with us and guide us each day.  We attempt to solve our problems with tangible, physical methods and neglect the spiritual origins of our problems.  A shaman, according the the Tungus tribe in Siberia is "one who sees in the dark.' (The Spirit world.)  Shamanism is a spiritual path (not a religion) which can be followed by anyone of any origin or religious affiliation.  It helps to direct our attention to the spiritual forces around us and to walk in harmony with all that is.