Is 'Emails Replied To' a subset of 'Emails Sent'?

Is 'Emails Replied To' a subset of 'Emails Sent'?

I have a simple question, Is 'Emails Replied To' a subset of 'Emails Sent'?

Per this Zoho article on email analytics, it provides the following:
  1. Sent - Only those emails that are sent from Zoho CRM and SalesInbox will be tracked. Emails that are sent via IMAP configuration, that is Zoho Mail or Gmail etc. will not be tracked.
  2. Replied - Emails to which the sales reps have replied.
I would assume if a Zoho user replies to an email, they are therefore sending an email back to the sender, thus my question's answer would be "yes". I want to confirm.

Thank you.