The operation of SSDs is based on flash memory chips. Therefore, an SSD does not have any of the mechanical components that an HDD has.
HDDs spin at high speed to read and write data. The faster they spin, the faster they react. However, they always need a minimum of time to find the place on the drive that contains the requested or to-be-archived data.
SSDs, in contrast, rely on their flash memory chips, composed of NAND logic gates, to accumulate the information. To perform this operation, they do not need to rotate any part of the disk, which allows them to have an immediate reaction time.
In addition, by eliminating mechanical components, SDDs require less power, reduce the weight and noise of the notebook, and minimize failures caused by disk spin-up and spin-down.