Associate Email Addresses with a Google Account:
Alternate email addresses are useful if you forget the password of your Google Account and now you can add more than one. In your account, click on Edit next to "Personal information" and associate additional email addresses with your Google Account. Note that you can't add email addresses already associated with another Google Account or Gmail addresses.
After you associate an email address with your account, Google sends a confirmation message to authenticate that the address is actually yours. An added benefit is that your other email addresses are connected to your account and Google can use this information: for example, Google Calendar shows you the invitations sent to any of the associated email addresses. You can also log in by using any of the additional email addresses.