Epson EQUITY 386SX/16 PLUS - Manual (Page 59)

All disks are divided into data storage compartments by sides,
tracks, and sectors. Double-sided diskettes store data on both
sides. On each side are concentric rings, called tracks, on
which a disk can store data.
A disk is further divided by sectors, which are similar in
shape to pie slices. The figure below provides a simple
representation of tracks and sectors.
Double-sided, double-density diskettes have either 40 or 80
tracks on each side, and double-sided, high-density diskettes
have 80 tracks on each side. Diskettes can have 8, 9, 15, or 18
sectors per track.
A hard disk consists of two or more platters stacked on top of
one another and thus has four or more sides. In addition, a
hard disk has many more tracks per side than a diskette, but
the number of tracks depends on the capacity of the hard
disk. The number of sectors depends on the type of hard disk.
Using Your Computer 3-7