HTTP responses have:

• a status code (200 OK! 404 not found!)
• headers
• a body (HTML, an image, JSON, etc)

Here’s the HTTP response from examplecat.com/cat.txt:

HTTP/1.1 200 OK
status
Accept-Ranges: bytes
Cache-Control: public, max-age=0
Content-Length: 33
Content-Type: text/plain; charset=UTF-8 Date: Mon, 09 Sep 2019 01:57:35 GMT
Etag: "ac5affa59f554a1440043537ae973790-ssl"
Strict-Transport-Security: max-age=31536000
Age: 0
Server: Netlify
[ASCII image of a cat, labelled "cat!" with a smiley face]

The first line, HTTP/1.1 200 OK is the status code. “200” is the status.

The lines from Accept-Ranges to Server are the headers.

The cat picture is the body.

There are a few kinds of response headers:

• when the resource was sent/modified:

Date: Mon, 09 Sep 2019 01:57:35 GMT
Last-Modified: 3 Feb 2017 13:00:00 GMT

• about the response body:

Content-Language: en-US 
Content-Length: 33
Content-Type: text/plain; charset=UTF-8
Content-Encoding: gzip

• caching:

ETag: "ac5affa..."
Vary: Accept-Encoding
Age: 255
Cache-Control: public, max-age=0

• security: (see page 25)

X-Frame-Options: DENY
X-XSS-Protection: 1
Strict-Transport-Security: max-age=31536000 
Content-Security-Policy: default-src https:

• and more:

Connection: keep-alive
Accept-Ranges: bytes
Via: nginx
Set-Cookie: cat-darcy; HttpOnly; expires=27-Feb-2020 13:18:57 GMT;