Which ctrl option defines which field is shown as the title of a record in the backend?

ctrl.label points to a field of the table whose value TYPO3 uses everywhere as the record title, for instance in the Content > Records module, in relation fields or in messages, e.g. 'label' => 'name'. The option is mandatory; label_alt lets you name fallback fields in case the main field is empty. It is easy to confuse with ctrl.title: that is the name of the whole table, such as "Product", not the title of an individual record. default_sortby only affects sorting, and descriptionColumn names a field for internal notes.