In music, the dynamics of a piece is the variation in loudness between notes or phrases. Dynamics are indicated by specific musical notation, often in some detail.
In terms of music pieces, dyanmic is esentially a varying detail of how loud a player should play. The signs include, and indicate:
< Crescendo, get louder.
> Decrescendo, get softer.
Dim. Is another word for decrescendo.
f is Forte, aka play loud.
ff is Fortismio, aka play louder then Forte.
FFF is also fortismio, also play louder then the previous.
p is Piano, play soft.
pp is pianismio, play very soft.
ppp is also pianismio, play extremley softly.
MP and MF mean playing at a medium level of soft or loud.
You will see these dynamics in music, and when possible follow them to a T.
Enjoy!