As both NAND flash memory manufacturers and users are turning their attentions from planar architecture towards three-dimensional (3D) architecture, it becomes critical and urgent to understand the characteristics of 3D NAND flash memory. These characteristics, especially those different from planar NAND flash, can significantly affect design choices of flash management techniques. In this article, we present a characterization study on the state-of-the-art 3D floating gate (FG) NAND flash memory through comprehensive experiments on an FPGA-based 3D NAND flash evaluation platform. We make distinct observations on its performance and reliability, such as operation latencies and various error patterns, followed by careful analyses from physical and circuit-level perspectives. Although 3D FG NAND flash provides much higher storage densities than planar NAND flash, it faces new performance challenges of garbage collection overhead and program performance variations and more complicated reliability issues due to, e.g., distinct location dependence and value dependence of errors. We also summarize the differences between 3D FG NAND flash and planar NAND flash and discuss implications on the designs of NAND flash management techniques brought by the architecture innovation. We believe that our work will facilitate developing novel 3D FG NAND flash-oriented designs to achieve better performance and reliability.