Send email action in the automation (both rules and workflows) is to facilitate the admin to deliver a one-off email without needing to use an email campaign or newsletter. The email content can be set right on the automation page (with the provided email editor) without requiring to navigate away to another screen or page.
Example of ideal usage of Send Email Action include the delivery of digital products, either attached directly to the email or providing a download link.
To compose a new email, click on the pencil icon to open up an email editor (which looks exactly like the email campaign editor). Alternatively, drop down the selection to choose from the emails written previously.
It is worth noting that there are 2 send email actions i.e “send email” and “send email to specific address”