What is email spoofing (brief intro, before deeper section)?

Email spoofing is when a message is forged to appear as though it was sent from someone else. Attackers do this by manipulating the From or Return-Path fields in the email header.

Spoofing can be used for phishing, scams, or impersonation attacks, and it is a major reason why SPF, DKIM, and DMARC exist.

It is like pirates raising a false flag to disguise their ship before approaching another vessel.