ASCII Armor is an encoding binary to text format representing encrypted message in ASCII format. Otherwords encrypted file is a binary file but it is saved as output ASCII armored text file.
As example below:
C:\Program Files\PGP Corporation\PGP Command Line>pgp --verify c:\users\Administ
rator\Desktop\Administrator1.asc -v
pgp:verify (3157:current local time 2013-11-13T00:28:19-08:00)
C:\Users\Administrator\Documents\PGP\pubring.pkr:open keyrings (1006:public keyr
ing)
C:\Users\Administrator\Documents\PGP\secring.skr:open keyrings (1007:private key
ring)
c:\users\Administrator\Desktop\Administrator1.asc:verify (3188:Version, Encrypti
on Desktop 10.3.0 (Build 8741))
c:\users\Administrator\Desktop\Administrator1.asc:verify (3188:Version, Encrypti
on Desktop 10.3.0 (Build 8741))
Decoding file c:\users\Administrator\Desktop\Administrator1.asc... 100% (Γ╕ѵÿ▒τ
îÑ)
c:\users\Administrator\Desktop\Administrator1.asc:verify (3113:data is armored)
Alg Type Size/Type Flags Key ID User ID
----- ---- --------- ------- ---------- -------
RSA4 pair 2048/2048 [---E-] 0xFE066637 Administrator <Administrator@pgp.lab>
RSA sig? [ -E ] 0x8481423B
RSA sig [ -- ] 0xFE066637 Administrator <Administrator@pgp.lab>
uid [- - ] Administrator <postmaster@pgp.lab>
RSA sig? [ -E ] 0x8481423B
RSA sig [ -- ] 0xFE066637 Administrator <Administrator@pgp.lab>
1 key found
c:\users\Administrator\Desktop\Administrator1.asc:verify (3055:data contains the
key 0xFE066637 Administrator <Administrator@pgp.lab>)
c:\users\Administrator\Desktop\Administrator1.asc:verify (0:verify complete)
C:\Program Files\PGP Corporation\PGP Command Line>
More information can be found here:
http://www.techopedia.com/definition/23150/ascii-armor
http://en.wikipedia.org/wiki/Binary-to-text_encoding
and also including this PGP forum thread https://www-secure.symantec.com/connect/forums/pgp-encryption-question
HTH