A Catch-all for email, usually refers to a mailbox on a domain that will “catch all” of the emails addressed to the domain that do not exist in the mail server. Configuring a catch-all address can help avoid losing emails due to misspelling.
For example: if firstname.lastname@example.org is configured to be the catch-all email address on jaamee.com, then any email sent to an email@example.com email address will be forwarded to firstname.lastname@example.org instead of being rejected as an Undeliverable message or Unknown User error.
You can only set one catch-all email address per domain. So it’s better to set the Administrator email address as the catch-all.