Check out the FAQ in Documentation/power/swsusp.txt.
Yes, the original purpose for the inclusion of the freezer code was to
support suspend-resume (mainly for laptops, but suspend-resume could
be useful in other circumstances too, see the FAQ).
Yes, the freezer is (proposed to be, at least) moving on from being
merely a suspend-resume-only thing to other usage scenarios, such as
kprobes and hotlpug.
-