What Is The Difference Between A Discovery And An Invention?

The basic rule of thumb is that a discovery is something which already exists, whereas an invention is something which has been created as being entirely new.
So for example, America was discovered (probably by the Vikings in the 10th or 11th Century).   America existed and so it could not be invented.  It had to be discovered.  
On the other hand a chocolate bar could be invented.  So although the peoples of Central America may have known about the cacao trees for hundreds of years, they were 'discovered' by Europeans, who brought back the cocoa beans from Central America.  These beans were then made into the same drink as had been made in America for years, again a discovery.  However, when the Europeans found new ways to grind up the beans and mix them together with sugar and cream or milk, then this created chocolate and so this is an invention !

Suppose you had married with a woman. That means you discover a woman and after a year that woman give birth to a child this child called invention.