Key point: A web request travels through DNS (name to IP), TCP (connection), TLS (encryption), and HTTP (request/response), and the browser is the environment that orchestrates all four. Every concept in this cheatsheet maps to one stage of that journey.
The Internet vs the Web
Term
Meaning
Internet
The global network of interconnected networks
Web
A service built on the internet (HTTP + browsers)
Protocol
An agreed format for communication
Packet
A small unit of data sent over the network
Router
A device that forwards packets between networks
The internet is the infrastructure; the web is one application running on it. Email, SSH, DNS, and streaming also use the internet.
IP Addresses vs MAC Addresses
Aspect
IP Address
MAC Address
Layer
Network (L3)
Data link (L2)
Format
IPv4: 192.168.1.10 / IPv6: 2001:db8::1
00:1A:2B:3C:4D:5E
Scope
Routable across networks
Local to a network segment
Assigned by
ISP, DHCP, or manually
Manufacturer
Changes
Can change
Fixed to hardware
IP Type
Meaning
Public
Globally routable
Private
Local only (10.x, 172.16–31.x, 192.168.x)
Loopback
127.0.0.1 (self)
Static
Manually assigned
Dynamic
Assigned by DHCP
Domain Names
Term
Meaning
Domain name
Human-readable name for an IP (example.com)
TLD
Top-level domain (.com, .org, .uk)
SLD
Second-level domain (example in example.com)
Subdomain
Prefix (www, api, blog)
FQDN
Fully qualified name (api.example.com.)
Registrar
Company that sells domain registration
WHOIS
Public record of domain ownership
URL vs URI Anatomy
Part
Example
Meaning
Scheme
https://
Protocol
Authority
user@api.example.com:443
Userinfo + host + port
Host
api.example.com
Domain or IP
Port
:443
Optional; default by scheme
Path
/v1/users/42
Resource location
Query
?page=2&sort=asc
Parameters
Fragment
#section
Client-side anchor (not sent to server)
A URI is the general identifier; a URL is a URI that also locates the resource. All URLs are URIs; not all URIs are URLs (mailto: is a URI, not a URL).
Web Hosting
Type
Description
Shared
Many sites on one server
VPS
Virtual private server slice
Dedicated
Entire physical server
Cloud
Virtual instances, scaling
Static
HTML/CSS/JS only, no server code
Serverless
Functions triggered on demand
Concept
Meaning
Web server
Software serving HTTP (Nginx, Apache, Caddy)
Document root
Directory served as /
Virtual host
Multiple sites on one server
CDN
Distributed caching edge network
DNS Resolution
Record
Purpose
A
Domain → IPv4
AAAA
Domain → IPv6
CNAME
Alias to another name
MX
Mail server
TXT
Verification, SPF
NS
Authoritative nameservers
Resolver Step
Server
1
Stub resolver (OS)
2
Recursive resolver (ISP/8.8.8.8)
3
Root server
4
TLD server (.com)
5
Authoritative nameserver
6
Answer cached
DNS uses UDP port 53. Caching occurs at browser, OS, resolver, and authoritative levels, governed by TTL.
HTTP Fundamentals
Method
Purpose
Body
GET
Retrieve
No
POST
Create
Yes
PUT
Replace
Yes
PATCH
Partial update
Yes
DELETE
Remove
Optional
HEAD
Headers only
No
Status Range
Meaning
1xx
Informational
2xx
Success (200, 201, 204)
3xx
Redirect (301, 302, 304)
4xx
Client error (400, 401, 403, 404, 429)
5xx
Server error (500, 502, 503)
HTTP is stateless; cookies and tokens carry state.
This cheatsheet is a map, not a textbook. Each row can expand into a chapter of its own. Use it to keep the layers in order: physical network → addressing → naming → protocol → client → tools. The request lifecycle is the thread that connects all ten topics, and the DevTools Network panel is where that thread becomes visible.
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