SDXC cards are SD cards but with a much higher capacity and faster processing speeds. They have a maximum capacity of 2TB (Terabytes).
An SDXC memory card is in fact the best supported memory card type amongst all video cameras that came out around the same time as the FDR-AX33.
The worst supported memory card type amongst similar types of camcorder is MicroSDXC.
SDHC cards are DS cards with a higher capacity of up to 32GB.