Any note or rest can have it's value (or duration) increased by adding a dot to right of the note.
 
For example:

1		Dotted Minim would have half the original value added, in other words if the original value was 2 counts then the addition of the dot would make it  3.
2		Similarly the Dotted Semibreve when originally having 4 counts would be increased to 6 with the addition of the dot.
3		Similarly a crotchet worth one count would have it's value increased to 1½ beats
4		The Dotted Quaver would have ¾ of a count  when the original value is one beat.
5		Dotted quavers are often joined to a semiquaver so that the pair equal one beat. Drummers often use this 'dotted rhythm' to produce a 'swingy' beat. Listen to Dvoraks 'Humeresque' for a famous example of this rhythm.