As is listed above, dynamics indicate the volume of the current music. However, it should be noted that, if yours is just one part of a larger ensemble, all dynamics will be relative. There is no set volume for Forte; it is just an appropriate contrast to how the piece is being played and what the instrumentation is like.


Dynamics:
Pianissimo          Ueber-Soft
Piano               Soft
Mezzo piano         Moderately soft 
Mezzo forte         Moderately loud 
Forte               Loud 
Fortissimo          Very loud 
Changes in Dynamics:
Crescendo           Increasing in loudness  
Decrescendo         decreasing in loudness  
Diminuendo          Same as decrescendo
Sforzando           Sudden loudness