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

A 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 increase it  to 3 counts. In the minim's case it like adding the value of a crotchet.

Similarly a crotchet worth one count would have it's value increased to 1½ beats, so in the case of a crotchet it is the same as adding the value of another quaver.

+ DOT

=

+

 

Dots can be used to increase the value of any note or rest.