3D NAND was developed in response to the scaling limitations of 2D NAND memory.
The layers in 3D NAND were flipped from horizontal to vertical orientation and strings of them were built to form a tower. By changing the direction of how the cells are configured created opportunity to increase storage capacity, reduce size of the storage area and reduce the power consumption to access the cells.
Honestly, it’s a complicated explanation to describe the changes between 2D and 3D NAND, but we found this awesome video from TechTarget. The video is very direct and to the point without over complicated explanations. Please watch it. 2min 20 seconds long.