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A virtual private network carries traffic through an encrypted tunnel over a public network so that a remote device or site behaves as though it were connected to a private one.

An intrusion detection system watches network traffic or host activity for signs of attack and raises alerts, while an intrusion prevention system sits inline and can block what it recognises.

A SIEM collects logs and events from across an organisation's systems into one searchable store, correlates them into alerts, and retains them for investigation and compliance.

A wireless LAN connects devices to a network over radio using the 802.11 family of standards, through access points that bridge the wireless medium onto the wired network and enforce the authentication and encryption that the shared airwaves demand.

TCP/IP is the family of protocols on which the internet runs: IP moves packets between addresses without guarantees, and TCP or UDP ride on top to deliver either a reliable ordered stream or fast unordered messages.

The OSI model is a seven-layer reference framework that separates networking into physical transmission, link, network, transport, session, presentation and application concerns, used to reason about where a problem sits rather than to describe any real protocol stack.

IaaS is the layer of cloud computing where you rent raw infrastructure through an API, meaning virtual machines, disks and networks, and take responsibility for the operating system and everything you install above it.

PaaS is a hosting layer that takes your source code and turns it into a running application for you, owning the machines, the runtime, the build, the routing, the certificates and the restarts, so that shipping becomes a push rather than a project.

Serverless computing runs your code only while an event is calling it: the provider conjures an execution environment on demand, throws it away afterwards, and charges for work performed instead of for capacity sitting idle.