What's the difference between postfix/smtp and postfix/smtpd

A bit confused when reading through the logs of my smtp/mail server, I'm turning this questions to you guys.

In the maillog files I'm seeing entries for postfix/smtp as well as postfix/smtpd. I can also see that there are possible settings for smtp as well as smtpd in the file main.cf

Trying to find some reasonable explanation through google search seemed to be impossible, so here is my question to you guys.

My server was kind of compromised and the spam mails where going through postfix/smtp and not smtpd. Please help me to understand. Thanks in advance!

postfix/smtpd - This is typically the SMTP daemon process for handling incoming mail and routing to the appropriate internal location.

postfix/smtp - This is typically the SMTP daemon process for delivering mail out to the world.

If you're seeing alot of postfix/smtp log entries, these would be all of the SMTP connections sending spam out to other nodes.

This blog post gives a pretty good overview of interpreting postfix logs.