Hide or show rows or columns
Hide columns
Select one or more columns, and then press Ctrl to select additional columns that aren't adjacent.
Right-click the selected columns, and then select Hide.
Note: The double line between two columns is an indicator that you've hidden a column.
Unhide columns
Select the adjacent columns for the hidden columns.
Right-click the selected columns, and then select Unhide.
Or double-click the double line between the two columns where hidden columns exist.
Source: Microsoft