Note & Rest Values.
The relationship of one to another - Each is "One-Half" value of the "Next Greater One".
Forexample: 1 Whole note = 2 Half notes = 4 Quater notes = 8 Eighth notes = 16 Sixteenths notes
Below image showing the notes and it's values.
The quarter note is a fourth (or a quarter) of a whole note.
Four quarter notes occupy the same amount of time as one whole note.
Two quarter notes equal the duration of a half note.
Notes smaller in duration than a quarter note have flags.
Each flag halves the value of a note. An eighth note has one flag.
Therefore, two eighth notes occupy the same amount of time as one quarter note.
A sixteenth note has two flags, halving the value again.
Two sixteenth notes equal the duration of an eighth note.
Four sixteenth notes occupy the same amount of time as one quarter note.
Although it is possible to have notes with three or more flags, they are seldomly used.