Confusion about a statement in the FAQ

[Anthony Papillion]

Hi Folks,

In the FAQ on the gnupg.org site there is a discussion about whether
it's acceptable to use PGP/MIME. The FAQ says yes and has the following
statement:

"Almost certainly. In the past this was a controversial question, but
recently there's come to be a consensus: use PGP/MIME whenever possible.
The reason for this is that it's possible to armor email headers and
metadata with PGP/MIME, but sending messages inline leaves this data
exposed."

I'm confused by this. What does it mean? What does 'armor the mail
headers" mean? Is this the same as 'encrypting' the mail headers or does
it mean something else?

Can someone explain this statement to me?

Thanks,
Anthony

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