Hi,

mast_col is a position that is define in some mainbody blocks like: mainbody-content-left.php, mainbody-content-right.php, one-sidebar-left-with-mastcol.php and one-sidebar-right-with-mastcol.php.

spotlight is a block but it's special block with 4 positions defined by default. The number of positions in spotlight block can be configured in the layout setting panel, you can select from 1 to 6, assign module position for each position in the spotlight block. In responsive layout configuration, you can resize positions in the spotlight block.

Gardner.