Difference between STMP address and STMP user name?

Hey Guys, Please tell me the difference so I can setup discourse. Mailgun setup is done just stuck at this point.

SMTP address is the common smtp domain of your provider

For european users, smtp address for mailgun is smtp.eu.mailgun.org and I believe for US users it is smtp.mailgun.org

SMTP user is the user you’ll set up in the Domain Setting area

Add a new SMTP user and Mailgun will generate a password