Select the cells, rows, or columns you want to hide
Right-click the selection
Click Hide
To hide cells only, format the cells with a custom number format like `;;;`
Select the cells
Press Ctrl+1
Go to Number
Choose Custom
Type `;;;`
Click OK
To hide formulas, select the cells
Press Ctrl+1
Go to the Protection tab
Check Hidden
Click OK
Go to Review
Click Protect Sheet
Set a password if needed
Click OK
To hide rows, select the row numbers
Right-click
Click Hide
To hide columns, select the column letters
Right-click
Click Hide
To unhide, select the surrounding rows or columns
Right-click
Click Unhide