Opt-In (or Subscribe)
To opt-in means to subscribe to email communications and join a particular company’s email list. It means that subscribers gave permission to the sender to email them. Recipients of email campaigns can often indicate what types of emails they wish to receive from the sender (e.g. sale notifications or newsletters).
Opt-Out (or Unsubscribe)
To opt-out simply means that you no longer wish to be on a particular company’s email list. By law mailers have to include an unsubscribe link in the body of an email campaign that they are sending.