How is a $ORIGIN directive used inside a DNS Zone File

[Harshith Mulky]

Why is a $ORIGIN directive used in DNS Zone Files?
Would my Zone Files not work if I do not have $ORIGIN directive?

I would need some examples on how this works, lets say

$ORIGIN .
[ What does $ORIGIN . mean?]
or


What is the difference here having 1.e164.arpa. in $ORIGIN [ as in example 1] or having it in NAPTR Records section [as in Example 2]
1.            $ORIGIN 1.e164.arpa.

or

2.               $ORIGIN 2.7.5.2.0.2.5.0.2.1.e164.arpa.
                          0            NAPTR    10 10 "u" "sip+E2U" "!^.*$!sip:2052025720 at 112.24.45.44!" .
                          1            NAPTR    10 10 "u" "sip+E2U" "!^.*$!sip:2052025721 at 112.24.44.44!" .
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