That was my first reaction when I first saw the acronym SDHC. I knew SD meant Secure Digital, which is a type of Flash memory card like the Compact Flash Card or the Sony Memory Stick. Apparently, the acronym SDHC means Secure Digital High Capacity. Since Secure Digital Cards are used in devices as diverse as PDAs, Digital Cameras and Camcorders, Gaming Consoles like the Sony PlayStation 3 and the Nintendo Wii, and even MP3 Players it is important to know whether your devices supports SDHC.
This is especially so since SD and SDHC Cards look physically alike:

If I was to buy the Kingston 8GB SDHC Memory Card, thinking that I could add 8 GB to my Palm TX I would have a problem – the Palm TX does not support SDHC cards. I could use the Kingston 2GB Secure Digital Card on a Palm TX, but not a 2 GB SDHC Card.

The reason is that SDHC cards use a different memory addressing method than standard SD Cards. SDHC cards only work in SDHC compatible devices, but standard SD cards work in both SD and SDHC devices.

To try to clarify which devices work with which Card, SanDisk has a website: SanDisk SDHC, which lists SDHC Compatible Devices. Of course since this is a SanDisk website, SanDisk Cards are recommended. For more neutral information, the SD Card Association has a webpage about SDHC Memory Cards.