How do molecules of a polar compound differ from those of a nonpolar compound?

Covalent bond = a bond in which the electrons are shared by the partner atoms. 

Polar bond = simply a type of covalent bond in which the electrons are 
shared but not equally. This happens when two different atoms come 
together, such a C and O. Each atom has a different ability to draw 
electrons to itself when it shares electrons (that drawing ability is 
called Electronegativity).