The sheet owner and licensed collaborators with Admin access to the sheet can hide a column to remove it from view while still keeping its content available in the sheet.
Though this functionality isn't available for rows, you can apply a filter to the sheet to hide rows based on criteria they contain. The filter will impact only your view of the sheet and other collaborators can apply their own filters as needed.
Hiding is useful when your goal is to format the sheet such that it displays only the most relevant information. Hiding is not a security feature. While collaborators with Editor and Viewer access won't be able to unhide the columns within Smartsheet, they can export the sheet to Excel or send it as an Excel attachment and un-hide the columns from that program.
Hide a Column
To hide a single column, hover over the column name and then click the More icon. Select Hide Column from the menu.
To hide multiple columns, hold down the [Ctrl] (Windows) / [Cmd] (Mac) key as you single-click on the header of each column you want to hide. Then click the More icon and select Hide Column.
The sheet owner and Admins can unhide all columns by clicking the More icon in any header and selecting Unhide All Columns. Unhide a single column by click-and-dragging the double-bar (which represents a hidden column) in the column header.