Tech glossary: from VLAN to MQTT

A brief explanation of the terms you encounter in guides and on forums. Is there a term you’re looking for that isn’t listed? Let us know via the Contact page.

A B C D E F G H I J L M N P R S T U V W Y Z

A

API. An agreed-upon way for programs to communicate with each other. A tool like our Whois uses this to request data from a registry.

B

Backup (3-2-1). A copy of your data in a different location. The 3-2-1 rule: three copies, on two types of storage, with one outside your home. See the 3-2-1 rule.

C

CGNAT. Carrier-grade NAT: your provider has multiple customers share one public IP address. This prevents you from forwarding ports to your home network. A VPN like Tailscale solves this. See WireGuard or Tailscale.

CIDR. The notation for a network with a slash, like 192.168.1.0/24. The number after the slash indicates how many bits belong to the network. Calculate it with the Subnet calculator.

Container. An isolated environment in which a single program runs with everything it needs. Lighter than a virtual machine. See Docker and LXC.

Cron. A scheduler on Linux that executes commands at fixed times. See the Cron guide.

D

DDNS (dynamic DNS). A service that makes a fixed name point to an IP address that changes, so you remain reachable at home with a name.

DHCP. The system that automatically assigns an IP address to devices on your network. Your router usually does this.

DNS. The phone book of the internet: it translates a name like geekstation.nl into an IP address. Look up records with the DNS lookup.

Docker. A program for running containers. See the Docker guides.

Docker Compose. A way to describe and start multiple containers together with a single file (compose.yaml). See the cheat sheet.

E

ESP32. An inexpensive microcontroller with built-in wifi and bluetooth, popular for custom sensors and smart-home devices. See the pinout.

F

Firewall. A filter that determines what network traffic is allowed to pass, on your router or on a computer.

G

Gateway. The device (usually your router) through which traffic to other networks, like the internet, passes.

GPIO. General Purpose Input/Output: pins on a Raspberry Pi or microcontroller that you can use as input or output. See the GPIO pinout.

H

HTTPS. Web traffic that is encrypted with a certificate. Check it with the SSL certificate check.

Hypervisor. Software that lets you run virtual machines, like Proxmox.

I

I2C. A serial bus that lets you connect many sensors and small displays to a microcontroller with two wires (SDA and SCL).

IoT (Internet of Things). Smart devices like lights, cameras, and sensors that are connected to a network. It’s better to put them on a separate network, see VLAN for your smart-home.

IP address. The address of a device on a network. See your public IP address.

J

JSON. A text format for exchanging data. Make it readable with the JSON formatter.

L

LXC. A lightweight type of container that behaves like its own Linux system; widely used in Proxmox.

M

mDNS. A way for devices to find each other on a network without a DNS server (for example for casting and AirPlay). Doesn’t work automatically across VLANs.

MQTT. A lightweight messaging protocol that many smart-home devices and sensors use. A central “broker” (like Mosquitto) distributes the messages.

N

NAS. Network Attached Storage: a device or server with drives that you can access over the network. See choosing a NAS.

NAT. Network Address Translation: your router lets all devices at home share the public IP address.

NFS. A protocol for sharing storage between Linux computers and servers.

NVMe. A fast type of SSD that sits directly on the motherboard or in an M.2 slot.

P

PoE. Power over Ethernet: power through the network cable, useful for access points and cameras.

Port. A number on which a service listens, like 443 for https. See the cheat sheet with ports.

Port forwarding. A setting in your router that forwards traffic from outside on a port to a device at home.

Proxmox. An operating system for servers that lets you manage virtual machines and containers. See the Proxmox guides.

PWM. Pulse-width modulation: a pin that rapidly turns on and off to dim an LED or control a servo, for example.

R

RAID. Using multiple drives together for speed or safety. It protects against a failed drive, but is not a backup. See the RAID and ZFS calculator.

Reverse proxy. An intermediary that directs traffic from outside to the right service inside your network, with https. See reverse proxy with https.

S

Samba (SMB). The protocol for file sharing with Windows and macOS.

SPI. A fast serial bus for displays and memory cards, with more wires than I2C.

SSH. Securely logging into another computer via the command line.

Subnet. A part of a network with its own range of IP addresses. See the Subnet calculator.

T

TLS / SSL. The technology behind https that encrypts traffic. SSL is the old name; nowadays TLS is used.

U

UART. A simple serial connection (TX and RX), used among other things for reading a console.

UPS. An uninterruptible power supply that keeps your server running temporarily during a power outage. See the UPS runtime tool.

V

VLAN. A virtual network within one physical network, to separate devices. See VLAN for your smart-home.

VM (virtual machine). A complete computer in software, with its own operating system. See your first virtual machine.

VPN. An encrypted connection to another network, for example to your home network. See WireGuard or Tailscale.

W

WireGuard. A modern, fast VPN protocol with a small configuration.

Y

YAML. A readable text format for settings, used by Docker Compose, Home Assistant, and ESPHome. Convert it with the YAML-JSON tool.

Z

ZFS. A file system with built-in protection against data errors, snapshots, and RAID-like configurations. See RAID and ZFS explained.

Zigbee. A low-power wireless network for smart-home devices, with a mesh in which devices relay to each other. See Zigbee in Home Assistant.

The explanation is intentionally brief. Want to know more? Follow the links to our guides and tools.