Internal hard drives are plugged into the back of a PC, another device like an external hard drive dock, or over USB and generally use 4.2 or 3.5-inch HDDs. HDD: A typical internal hard drive is an enclosed housing with spinning disks inside, typically used to store computer data. They are large (in terms of capacity) and slow; however, they offer low costs per gigabyte.
SSD: An SSD performs better than a typical HDD in most cases because it accesses data faster, which makes it perfect for operating systems and programs that require quick responsiveness. In addition, an SSD does not suffer from storage space limitations like HDDs and can be larger (up to 2TB) without incurring extra costs. While SSDs are more expensive up front than HDDs, the benefits may well justify the cost in the long run. For example, an 80GB SSD will last 10 years compared to only 5 years for a comparable 80GB HDD