auto vs star - in xaml, briefly

<ColumnDefinition Width="10*"/>
<ColumnDefinition Width="*"/>

... in wpf (not Silverlight) means that the first column is 10x wider than the second. It's like saying "10 parts column 1, and 1 part column 2." The cool thing about this is that your columns will resize proportionally.

////////////////
//eat up all available space that enclosing container has
<ColumnDefinition Width="*"/>

////////////////
//Take up as much space as the contents of the column need
<ColumnDefinition Width="Auto"/>

///////////////
//Fixed width: 100 pixels
<ColumnDefinition Width="100"/>