Each layer contains traces and circuitry, which facilitate the movement of data. In general, higher quality memory modules use PCBs with more layers. The more layers a PCB has, the more space there is between traces. The more space there is between traces, the lesser the chance of noise interference. This makes the module much more reliable.
Most memory chips have black or chrome coating, or packaging , to protect their circuitry.
On some memory modules, these leads are plated with tin while on others, the leads are made of gold. The magnifying glass shows a layer of the PCB stripped away to reveal the traces etched in the board. Traces are like roads the data travels on. The width and curvature of these traces as well as the distance between them affect both the speed and the reliability of the overall module. Take a look at the different chip packages below, so you can see how they differ.