The Protect Sheet or Protect Spreadsheet commands prevent changes from being made to cells in the sheets or to sheets in a document. As an option, you can define a password. If a password is defined, removal of the protection is only possible if the user enters the correct password.
Choose Tools - Protect Sheet
Choose Tools - Protect Spreadsheet
Protects the cells in the current sheet from being modified.
Protects the sheet structure of your document from modifications. It is impossible to insert, delete, rename, move or copy sheets.