> Why use the "else if" if you can just put another "if" statement in there?
The else if construct stops when the first true condition is found.

Code:
if ( grade == 'a' )
else if ( grade == 'b' ) 
else if ( grade == 'c' )

Against
if ( grade == 'a' )
if ( grade == 'b' )
if ( grade == 'c' )
If the grade was 'b', then using else if, the grade == 'c' comparison is skipped, because a successful match was made.