NAND flash has a much higher storage density. You can store a lot more memory in the same size chip with NAND flash, which means higher capacity flash drives in the same size and cost. The downside is that you can’t easily access individual bits randomly, and you can only erase the memory a block at a time, so the read and write times are worse than with NOR flash.
NOR flash allows user to directly read a cell whereas NAND flash reads a page.Therefore access times are much faster in nor flash than nand flash.
NOR and NAND flash get their names from the structure of the interconnections between memory cells. In NOR flash, cells are connected in parallel to the bit lines, allowing cells to be read and programmed individually. The parallel connection of cells resembles the parallel connection of transistors in a CMOS NOR gate. In NAND flash, cells are connected in series, resembling a NAND gate. The series connections consume less space than parallel ones, reducing the cost of NAND flash. It does not, by itself, prevent NAND cells from being read and programmed individually.
