The difference between a hard disk drive (HDD) and a solid state drive (SSD) lies in the different functionality and the resulting speed and price difference. The HDD is a magnetic storage medium that uses moving components in the form of read and write heads.
The SSD does not have any moving parts and thus does not generate any noise. Instead, it uses flash memory, just like in USB sticks or SD cards. In the following table I explain the advantages of each storage medium:
HDD
SSD
A lot of memory for little money.
Fast and quiet.
High storage capacities possible.
Compact and lightweight.
Long life.
Shock resistant.