Most likely, someone mistakenly tried to register using your email address. Do not click the link in the email. If you don’t click the link, the account will not be confirmed. An unconfirmed account can remain on the site for a maximum of three days, but it can’t be used to send messages, write on Walls (timelines), post in discussions, poke, tag friends in photos or notes, comment on content, join groups, or like pages. After three days without the email owner’s confirmation, the account will become inaccessible.
If someone created an account to impersonate or imitate you, learn more about how to report this.