A:Answer The difference between the different classes is related to the guaranteed minimum write speed in MB/s - the suitability is as follows (from SD association):
Class 2 : H.264 video recording, MPEG-4, MPEG-2 video recording
Class 4: MEPG-2 (HDTV) video recording, digital still camera (DSC) consecutive photo shooting
Class 6: Mega-pixel DSC consecutive photo shooting, professional video camera
Class 10: Full HD video recording, HD still picture consecutive shooting