font: 10px/1.6 verdana, arial; ??

Hi guys...

Just a small query... what is the difference between using these 2 different methods of styling text? (And on 2. how do i apply bold in the same line...)

Thanks

1.
font-family: Arial, Verdana;
font-weight: bold;
font-size: 11px;

2.
font: 10px/1.6 verdana, arial;