Memory card

Memory cards are solid-state electronic flash memory data storage devices used with cameras, handheld and laptop computers, phones, music players and other electronics.
They offer re-recordability, power-free storage, small form factor and rugged environmental specifications.

Name	Acronym	Form Factor
CompactFlash I	CF-I	43x36x3.3mm
CompactFlash II	CF-II	43x36x5.5mm
SmartMedia Card	SMC	45x37x0.76mm
Multi Media Card	MMC	32x24x1.5mm
Secure Digital Card	sD	32x24x2.1mm
Extreme Digital Card	xD	20x25x1.7mm

Since all sorts of EEPROM devices only allow a finite number of write cycles, some of these cards incorporate wear levelling algorithms to spread the wear and to avoid wearing out specific places which are often written to.

(I am not sure here) CompactFlash uses wear levelling while SmartMedia does not have any intelligence built in and presents the raw chip on its external interfaces.