What makes a coffee maker "smart"?

It varies widely. Some models in this category (like the Keurig K-Café SMART) offer genuine WiFi connectivity and app control, while others marketed as "smart" simply pair with an Alexa-compatible smart plug or offer 24-hour programmable scheduling. Decide whether you want true app/voice control or just a reliable delay-brew timer before you buy, because the price gap between those features is large.