Attendees automatically receive a receipt email upon completing their checkout.
Once an attendee has registered for your event and paid for their ticket they will receive a receipt via email.
Here's how the content of that email would look:
You can check that this event email template is turned on, or turn it off if you prefer it not be sent, by going to Event Setup > Email Templates > click the 3 dots (...) to the right of the ‘Payment Receipt’ email > Edit record and checking or unchecking the box under Active?
If attendees need a more detailed receipt, including payment method, contact us at firstname.lastname@example.org with the attendee email address and the email address that you would like this to be sent to (if different).