Phishing is an attempt to steal sensitive information like passwords and banking details. A common phishing scam involves the victim receiving an email stating that your Apple ID was used to sign into iCloud. The email appears to be from Apple. If you look at the sender’s email address and it is not from Apple, this is a scam (example below). Do not open links from the email and do not respond.

To learn more and report Apple phishing scams, follow this link to Apple.com.
Other information obtained from Parallels.com.