Every email address is something like this ... local-part@domain
the name after the @ symbol is a domain name that represents the administrative realm for the mail box and the part before the @symbol identifies the name of the mailbox.
twrigley(local portion)@ gumchewer.biz(domain)
twrigley is the local portion which indicates to the mail server which mailbox the message is from or to.This portion is only important to gumchewer mail server which is why it is called local.