A dot placed after a note increases the duration of that note by half its value.

For example, a half note is normally held for the equivalent of two quarter notes.  Therefore, a dotted half note would be held for the equivalent of three quarter notes.  Dotting a quarter note, which is normally held for the equivalent of two eighth notes, would increase its duration to the equivalent of three eighth notes.

Following is a chart that shows the equivalent values of dotted notes.

Count and clap the rhythms in the following examples.

Notice the time signature in the following example.  The top number tells you that there are six beats in a measure.  The bottom number tells you that an eighth note gets one beat.  Therefore, a quarter note will get two beats, and a dotted quarter note will get three beats.

This example also uses a dotted quarter note.  But in this case, the time signature is 3/4, so the dotted quarter note will receive 1 1/2 beats.

This next example uses a dotted eighth note, which receives the equivalent of three sixteenth notes.  Notice the beaming on the dotted eighth - sixteenth note group