The grid has to be specified using the 'grid template-columns and rows' properties giving the number and width of each.
Use the grid-column property to specify in which column to place an item, and how many columns the item will span.
Use the grid-row property to specify on which on to place an item, and how many columns the item will span.
This property is a shorthand property for the grid-column-start and grid-column-end properties.
Item1 will start on column 1, and 2 on column 1 (reversed to make the point: