The main difference between SSD (Solid State Drive) and HDD (Hard Disk Drive) lies in their data storage technology. SSDs use flash memory to store data, which allows for significantly faster data access and transfer speeds compared to HDDs, which rely on mechanical rotating disks to read and write data. Consequently, SSDs offer improved performance, durability, and lower power consumption. However, SSDs typically come at a higher price per gigabyte compared to HDDs, making them less cost-effective for larger storage needs. This difference influences consumer choices based on performance versus capacity requirements.