This version consists of the motherboard only. Recommended if you are building your own CNC machine from scratch.
"Motherboard + Expansion Card" version
This version includes the motherboard and the expansion board. The latter is required if you want to use the additional I/O lines and the LPT-style connection. Recommended if you wish to convert an old CNC machine from Mach3-LPT style to ESP32-GRBL style.
"Embedded stepper drivers" version
In this case, the expansion board also mounts the stepper drivers, which must be duly cooled with a heat sink. Recommended if you want to build a desktop CNC machine.