SPF Records are shorthand for the Sender Policy Framework (more information here standard which is being implemented by a number of hosting companies on the Internet.

Email "spoofing" happens when a spammer sends out spam to other people using completely unrelated servers and your email address as the return address. In this process, they are neither using your account nor using our server to send the email, but they forge the "reply to" address to be another address - in this case, yours.