Could someone elaborate the way Dehn suggested to make a Poincaré's homology sphere using "Dehn surgery"?

Question

They say it can be made by extracting something from a three dimensional sphere and sewing back, but I just can't understand...

Answer 1

Read about it at Wikipedia ... follow up the hot-links & references (these will help assist your understanding).

If you still don't 'get it', don't worry about it (go look at your Finances instead == how wealthly or poor you are going to be when you Retire is a LOT more important :-) )