About
In a hard disk, Data is written to and read from the surface of a platter by a device called a head. Naturally, a platter has 2 sides and thus 2 surfaces on which data could be manipulated; usually there are 2 heads per platter–one on each side, but not always. (Sometimes the term side is substituted for head, since platters might be separated from their head assemblies; as is definitely the case with the removable media of a floppy drive.)