[The Wikipedia article on surgery theory][1] explains this! In addition, the Edinburgh [Surgery Theory Study Group][2] provides all kinds of surgery-related materials, including [YouTube videos][3] (not for the squeamish).

 


  [1]: http://en.wikipedia.org/wiki/Surgery_theory
  [2]: http://www.maths.ed.ac.uk/~s1057008//surgerygroup/
  [3]: http://www.youtube.com/user/SurgeryGroup