How to use heal eadges in solid works. How it works
It is used when you opening a file translated from other software.
For example someone modeled a part in Catia, He saves it universal format like step - I could open it in SolidWorks but if the part is very complicated -translated model have a errors- there are holes between surfaces or something.
If I have to make a 2d drawing of this poart or modify it i need to heal edges.