What does shrapnel do to the body?

Can you elaborate on the damaging effects that shrapnel can have on the human body when it enters during a conflict or explosion? Specifically, how does it cause internal injuries, what types of injuries might it inflict, and what are the potential long-term consequences of being hit by shrapnel? Additionally, are there any treatment options available for those who have been injured by shrapnel, and what is the prognosis for their recovery?