This glossary explains VPN, DNS, IPv6, CGNAT, kill switch, split tunnelling, WireGuard, OpenVPN, proxy, Tor, ZTNA and logging for UK readers and UK network context.
UK practical context
Area
What to check
A good first step
VPN / tunnel
Encrypted routed path to a server
Does not guarantee anonymity
DNS / resolver
Translates names to network addresses
Can follow a different path from web traffic
CGNAT
Carrier shares public IPv4 addresses
Commonly affects inbound access and gaming
Kill switch
Blocks fallback when the tunnel fails
Must be tested on the real device
No-logs
Provider claim about defined data categories
Read scope, retention and audit evidence
Where to start
Identify the layer: account, app, device, network or provider.
Check whether the term describes a protocol, feature or marketing claim.
Read provider-specific implementation details.
Verify behaviour with a safe test.
Use linked technical guides for configuration.
Treat legal and compliance terms as context-specific.
Common questions
Is a proxy the same as a VPN?
No. A proxy commonly covers selected application traffic; a VPN can route more device traffic.
What is CGNAT in the UK?
It is carrier-grade address sharing used by some broadband and mobile networks.
Does no-logs have one standard meaning?
No. Providers define categories differently; inspect policy and evidence.
This page covers the usual case; your device, provider or network may behave differently. Follow UK law, account eligibility, rights, administrator policy and platform terms.
VPN glossary for UK users: protocols, privacy and networking terms
Short answer
A VPN glossary matters because most privacy problems start with misunderstood words. Terms like DPI, WireGuard, kill switch, obfuscation, and no-logs shape how a VPN really behaves. This page helps you search those terms fast, connect them to related concepts, and jump straight into deeper guides when you need more than a definition.
Disclosure: We may earn affiliate commissions if you buy via our links. This helps fund testing. See Disclosure.
The glossary is not here to impress people with jargon. It is here to make terms usable. If you already know the basics, the value is in seeing how one concept touches another: VPN Encryption connects to protocol choice, protocol choice connects to speed, and speed still means nothing if DNS leaks or broken handshakes ruin the setup.
Quick definitions
These are the terms people usually reach for first when they want a fast answer, not a long lecture.
Tap a cluster and the glossary search box will jump toward the right group of terms.
The practical chain is simple: protocol and routing choices shape privacy outcomes, and privacy outcomes shape whether the VPN works well for streaming, remote work, or restrictive networks.
The term finder below comes from the earlier glossary page structure and keeps the strongest part of that older build: live search, connected terms, A - Z navigation, and expandable term cards. It has been moved into the newer BBC iPlayer-style layout so the page stays consistent with the rest of SmartAdvisorOnline.
Term finder and concept guide
Search, filter, open any term, and explore related concepts with lightweight diagrams.
0 terms0 shown
No terms found. Try another keyword, or browse categories.
Tip: When troubleshooting buffering, ads, or geo-blocks, verify DNS and WebRTC first using our
Leak Test Tool.
Term
CategoryLevel
Why it matters in 2026
Misconception:
Reality:
Related terms
Where to go next
Once a term clicks, the next step is usually practical. Definitions matter only if they help you fix something, choose better settings, or understand what your VPN provider is actually offering.
Related guides
These pages connect directly to the glossary terms above and use the same site structure as your recent BBC iPlayer-style articles.
How to use this glossary when diagnosing a VPN problem
A glossary is only useful if it helps you make a decision. When a VPN fails on a UK broadband or mobile connection, start by translating the symptom into a small set of technical terms. Buffering usually points towards latency, jitter, packet loss, congestion or a weak route. A location warning points towards IP reputation, DNS mismatch, IPv6 exposure or account-region signals. A sudden disconnect points towards protocol switching, sleep behaviour, captive portals, router firmware or mobile handover.
For streaming issues, the most useful terms are DNS, IPv6, WebRTC, latency, jitter and cache. For public Wi-Fi, focus on captive portal, kill switch, DNS resolver and local network exposure. For remote work, the practical vocabulary changes again: MFA, split tunnelling, access control, device posture, audit trail and least privilege. Reading the terms in that order stops the page from becoming a dictionary and turns it into a troubleshooting map.
UK examples that make the terms less abstract
On home broadband, a router from BT, Sky, Virgin Media, TalkTalk or Vodafone can influence DNS behaviour, IPv6 availability and Wi-Fi stability before the VPN provider is even involved. On mobile networks such as EE, O2, Vodafone and Three, the same VPN app can behave differently because roaming between 4G, 5G and Wi-Fi changes the path under the tunnel. That is why a clean speed result is not the whole answer. A stable VPN connection also needs predictable DNS, low jitter, sensible protocol choice and a kill switch that behaves correctly when the network drops.
Use the glossary alongside the VPN leak test, the VPN speed test and the streaming diagnostic. If a term still feels unclear after running a tool, the tool result usually tells you which guide to read next.
Decision map: which term matters for which UK problem?
If a website shows the wrong region, read the entries for IP address, DNS leak, IPv6 and WebRTC before reading anything else. If live sport buffers, read latency, jitter, packet loss and congestion. If a work app refuses to connect, read split tunnelling, MFA, access control, device posture and captive portal. If a mobile VPN drops while travelling, read roaming, handover, WireGuard, IKEv2 and kill switch.
UK readers should also pay attention to broadband and mobile context. Home routers from BT, Sky, Virgin Media, TalkTalk and Vodafone can shape DNS and Wi-Fi behaviour. Mobile networks such as EE, O2, Three and Vodafone can change route quality as a phone moves between 4G, 5G and Wi-Fi. The glossary terms are not abstract labels; they are the vocabulary you use to isolate the failing layer.
When a term appears in several guides, treat it as a signal worth testing. DNS appears in streaming, privacy, router and leak pages because it is one of the most common ways a connection reveals more than the user expects. Jitter appears in speed and sports-streaming pages because average download speed alone does not explain live playback. A glossary earns its place when it helps you choose the next test.
