Interpreting phpinfo() HTTP Response Headers section

[Newba]

Hi,
I'm trying to research differences between two servers, one of which
seems to be URL-encoding user input.
I ran phpinfo() on both; one difference that stood out is the
"Response Headers" section.
On one server, it looks like this:
X-Powered-By PHP/5.1.6
Connection close
Transfer-Encoding chunked
Content-Type text/html; charset=UTF-8
But on the other server, it looks like this:
X-Powered-By PHP/5.1.6
Cache-Control max-age=1
Expires Fri, 11 Sep 2009 20:28:51 GMT
Vary Accept-Encoding
Content-Encoding gzip

I understand that the header information affects how the browser
interprets the page, but I don't fully understand how the server setup
affects what shows up in this section of phpinfo() or what that really
means for the site (if anything).
I also tried doing this to get more information:
print_r(ini_get_all());
From that, I was able to see see some minor differences between the
servers' ini settings, but none of them stood out as being related to
Response Headers (or to the fact that one of the servers is URL-
encoding user input).
Does anyone have knowledge to share about how to interpret this
information?
Many thanks in advance!