Here is the explanation
Egg shells contains 95% of Calcium carbonate
While vinegar mainly contains acetic acid (ethanoic acid)
When the reaction bewteen calcium carbonate and enthoic acid occurs...
Observation of products
Colourless gas (carbon dioxide) bubbles evovled
The egg shells (calcium carbonate) dissovled to the solution
Thus the egg shell of the egg is nearly all gone with colourless gas bubbles evovled