When in Delete Selection Mode, commands that insert text into the buffer first delete any selected text. Delete Selection Mode is a global editor setting. It is off by default with Emacs keys, and is on by default when using macOS editor emulation.
Delete Selection Mode Editor Command
Arguments: None
Key sequence: None
Toggles Delete Selection Mode, switching it on if it is currently off, and off if it is currently on.
Editor User Guide (Macintosh version) - 01 Dec 2021 19:35:09