What's the difference between a smart light socket and a smart bulb?

A smart light socket is an E26/E27 adapter that screws into an existing fixture; you then screw any regular bulb into the adapter, and the adapter handles Wi-Fi connectivity, scheduling, and voice control. A smart bulb has the electronics built into the bulb itself. Sockets are useful when you want to keep a specific bulb (e.g., a vintage Edison or a high-CRI LED) or when smart bulbs don't fit a fixture, but they usually only support on/off and timers, not dimming or color.