RS-MMC stands for Reduced-Size MultiMediaCard. It is only about half the size of a standard MultiMediaCard (MMC), with average dimensions of 24mm x 18mm x 1.4mm. The variety of the MMC card was introduced in 2004 and designed for smaller products, mainly portable devices. While they are much smaller, they are still typically MMC cards for all intent and purposes, but achieve a smaller form factor by using a simple mechanical adapter to elongate the card.
The maximum capacity currently available for RS-MMC is 2GB. RS-MMC is used with Symbian Series 60-based mobile phones, with Nokia and Siemens being the biggest hardware licensors of RS-MMC. Nowadays Nokia prefers the microSD or miniSD cards for its products however, and seems to be largely abandoning the RS-MMC format.
MultiMediaCard --> Original MMC card.
DV-MMC --> Stands for Dual-Voltage MultiMediaCard, a substantial change to MMC that introduced dual-voltage cards.
MMCplus --> Introduced in 2005, MMCplus runs at higher speeds. Also marketed as "MMCmobile".
MMCmobile --> Introduced in 2005, MMCmobile runs at higher speeds. Also marketed as "MMCplus".
MMCmicro --> Similar to the microSD format, this small form factor MMC card is thinner and smaller than RS-MMC.
miCard --> Introduced in 2007, this version of the card technically has a maximum capacity of 2 Terabytes (2TB).
SecureMMC --> SecureMMC is to provide a secure removable storage to secure applications using as MMC card.