Glossary

Compute Module (CM4/CM5) — a Pi without ports, on a small board meant to be built into custom products. For manufacturing, not hobbyists.

GPIO — General-Purpose Input/Output: the 40-pin header for connecting buttons, sensors, LEDs, and HATs. The Pi's superpower over a regular PC.

HAT — Hardware Attached on Top: an expansion board that plugs into the GPIO header (NVMe HATs, sensor HATs, DAC HATs...). The Pi 5's PCIe HATs are the current hot zone.

headless — running without monitor or keyboard, administered over SSH. How nearly every Pi server runs.

microcontroller (MCU) — a chip that runs one program directly on hardware: no OS, kilobytes of RAM, milliwatts of power. The Pico, not the Pi.

Raspberry Pi Imager — the official SD-card flashing tool (Windows/Mac/Linux). Handles OS selection, SSH enablement, Wi-Fi, and user setup before first boot.

Raspberry Pi OS — the official OS: Debian Linux tuned for Pi hardware. Comes in full (desktop), Lite (no desktop), and 64-bit variants.

raspi-config — the Pi's text-menu configuration tool (sudo raspi-config): hostname, SSH, GPU memory, boot order, localization.

single-board computer (SBC) — a complete computer on one board: CPU, RAM, USB, networking. The Pi 5/4/Zero are SBCs; the Pico is not.

throttling — the Pi slowing itself down to avoid overheating (at 80°C) or undervoltage. Check history with vcgencmd get_throttled.

undervoltage — the power supply sagging below what the Pi needs, causing random crashes. The lightning-bolt icon, or a nonzero vcgencmd get_throttled.