A database write is an action that changes information saved in a database. It might add a new record, edit an existing one, or remove one.
Imagine a library card catalog. Reading a card does not change it, but adding a new book or correcting its details is a write.
Because writes change saved information, apps often check the values first and may keep a record of the change. If a write is made by mistake, it might be difficult to undo without a backup or another recovery method.