Socket cards are typically the LED driver. There are two basic types: Constant Current (CC) where the current is regulated and the voltage varies depending on what the LED draws, and Switched Voltage (SV) where a fixed 48V is sent to the device and its internal regulator accepts the 48V directly.
Fused Voltage (FV) socket cards are similar to Switched Voltage (SV). Ceiling Fans, Exhaust Fans, Track Lights, Addressable Lights, and 24V Strip Light Controllers are examples where the FV cards are used. These cards send 48V power to the wire and the end devices manage how the power is used. The self-healing eFuse feature protects the wiring in the walls. Most fixtures and devices connected to FV cards are Addressable, meaning they are controlled by the communication protocol in the wire. These are great for color RGB holiday lights, track lighting, ceiling fans, exhaust fans, and stair lights.