NAND flash memory can be sub-divided into 2 broad categories SLC and MLC.

SLC is an abbreviation of 'Single-Level Cell':

SLC memory stores one bit in each cell, leading to faster transfer speeds, lower power consumption and higher cell endurance. The only disadvantage of Single-Level Cell is the manufacturing cost per MB, meaning that the SLC flash technology is used in high-performance memory cards.

MLC is an abbreviation of 'Multi-level Cell':

MLC memory stores three or more bits in each cell. By storing more bits per cell, a Multi-Level Cell memory card will achieve slower transfer speeds, higher power consumption and lower cell endurance than a Single-Level Cell memory card. The advantage of Multi-Level Cell memory card is the lower manufacturing cost. The MLC flash technology is used mostly in standard memory devices. The Multi-Bit Cell, MBC, is a similar technology to the Multi-Level Cell but stores only two bits per cell.