It extends the note for half it's value for example: a dotted quarter is worth one and an half beats.A dotted half note is worth three beats.a dotted whole note (which is rare) is worth six beats....
If the dot is next to the note head, it means to add to the note half the duration of the note without the dot So if a quarter note is dotted, it is held for the duration of 3 eighth notes.
A dot beside the note means that you had on half the value of the note. Sounds weird, but to take it simplier. Say you have a minum (2 beats) which has a dot on it. You add on 1 beat so that the note...
That is called a staccato marking. It's a stylistic marking that mean you should play the note separated from those around it; there should be a little space between each note.