Spoofing is the technique of faking a digital identity (an email address, a phone number, an IP address or a website) so the victim believes they're dealing with someone trusted. It's the basis of many email and phone scams, because the message appears to come from an executive, a bank or a real vendor.
Related term in this glossary: SPF, DKIM and DMARC
email spoofing, IP spoofing, domain spoofing, caller ID spoofing