What is the meaning of theClass Speed Rating shown on SDHC cards?

What is the meaning of the"Class Speed Rating" shown on SDHC cards?

Category : Specification / Capacity / Performance

The SD Association defines 4 speed classes to help users identify SDHC card speed and performance. The class speed rating specifies a minimum sustained read/write speed (Class 2: 2 MB/s; Class 4: 4 MB/s; Class 6:6 MB/s; Class 10: 10 MB/s). You can identify the performance of your memory cards and host devices according to the Speed Class Logo.

Class/ Transfer Rate	Min. Read Rate	Min. Write Rate
Class 2	2 (MB/sec)	2 (MB/sec)
Class 4	4 (MB/sec)	4 (MB/sec)
Class 6	6 (MB/sec)	6 (MB/sec)
Class 10	10 (MB/sec)	10 (MB/sec)