It is a non-volatile storage device that stores data using magnetic storage technology. It consists of rapidly rotating platters coated with magnetic material, where data is written and read by magnetic read/write heads.
Data is stored as magnetic bits on the platter surface. Each bit represents either 0 or 1 based on magnetic polarity. The read/write head uses electronmagnetic fields to change or detect these magnetic orientations, allowing data to be written and read.