If you mean the two round holes in an electrical plug, they are not usually “magical” features—they have practical electrical purposes.
- On a two-pin plug, the two holes are typically the contacts/openings where the socket’s pins enter. They connect the appliance to the two conductors of the electrical supply.
- In some plug designs, the holes can also be used by the socket mechanism for locking, alignment, or safety features.
- If you mean the two small holes near the ends of the metal prongs on certain plugs, those can have other purposes, such as helping manufacturers with assembly or allowing certain socket mechanisms to grip the prongs.
- The exact purpose depends heavily on the country and plug type.
If you can upload a photo of the plug, I can identify exactly what those two holes are for.