What is it ?
A Hard Drive (HDD) is inside the computer and it stores and retrieves all of your digital data , its located where the cd slot is. Rotating disks with metal are the parts that help save the data,the Hard Drive retains its data even when the computer is turned off.
The external HDD is exactly the same as the internal only that the external can be plugged inside the computer and the internal is already inside.
General Info about the HDD
The HDD was first introuduced by the IBM in 1956 , more than 200 companies have produced the Hard Disk Drive.