What is Arduino: a brain the size of a matchbox

Arduino is a small board with a microcontroller (classic: Arduino UNO ~€25, clones from ~€5). It does one thing: read signals on pins and switch other pins per your program. That is enough to blink lights, measure temperature, spin motors and open a garage door. Unlike a computer: no screen, no Windows — but instant start, 0.05 W draw, 20-year lifespan. The program is called a Sketch, written in the free Arduino IDE and uploaded via USB.

• ●UNO for learning; Nano, small, for projects; Mega when you run out of pins
• ●Pins: 14 digital (D0–D13) + 6 analog (A0–A5) + power 5V/3.3V/GND
• ●ESP32 — the "big brother" with Wi-Fi and Bluetooth for ~€10