with lisp structural edditing you are editing blocks of code, as opposed to characters. in fact it is the use of s-expressions that makes this possible. here is a simple example. immagine you have a list, two elements just outside it, and your cursor is just after the second element:

  Python: [x,y,z] 1,2
  Lisp: '(x y z) 1 2

and lets say you want everything in the list st

  Python: [x,y,z,1,2]
  Lisp: '(x y z 1 2)

in python it would take me about 5 keystrokes to achieve that, while with paredit in lisp it takes 2. this is just a very simple example of the most basic paredit operation. extending this approach to your whole source file and treating whole blocks of code similarly to the above examlle i find really handy