I use Secure Digital High Capacity (SDHC) memory cards (or their mini or micro siblings) in a range of devices. I understand storage; 8GB stores twice as much as 4GB. But I have little understanding of speed ratings like Class 2, 4 or 6.
Tom’s Hardware, my primary source of information on hardware, demystifies SDHC memory cards, and compares cards from different manufacturers, in 13 SDHC Memory Cards Reviewed : SD Memory Cards for Professionals. The conclusion? Well, I don’t want to promote reader laziness. Read the article 🙂
Source (including picture): Mobile Devices Today