An important aspect of any style of music is the use of dynamics, which means variations and contrasts in volume. The most obvious way of changing dynamics is the use of accents. An accent is a note or chord suddenly played louder than the preceding notes. An accent is indicated by a wedge shape above or below the note. Here are some examples of accents.
Example 78 is played quietly the first time and louder on the repeat.
This one uses contrasting dynamics within a phrase. Notice the dynamic markings p (meaning soft) and ff (meaning very loud.)