Choose from a list...

Displays the column selection button's list of grid columns, where you may choose columns to show in the grid by check marking them.

Show Column Chooser

Displays the Column Chooser window.

You may choose columns to show/hide in the grid by dragging column headings from/to the Column Chooser.

Best fit current column

Makes the currently-selected grid column wider or narrower, to fit the data it displays.

Best fit (all columns)

Makes all grid columns wider or narrower, to fit the data they display.