If you share a workbook with others and want to stop them changing the sheet cells you can protect the sheet. By default all cells are protected. If you want to allow them to enter information in some cells, but not others, then you need to unlock the cells to allow them to be changed.
Select the cells, go to format cells, untick the Locked.
Protect the worksheet, (you can choose to add a password) and your locked cells are safe, leaving the unlocked cells free for information to be entered.