In music notation, dynamics describe the volume or loudness of the music, both fixed and changing. They are generally positioned below the staff or in the middle of a grand staff, and with a few exceptions are always marked using one to three letters in a stylized font.
When used with a staff, they look something like this (piano, crescendo and forte markings are used here):
/\
---| /----------------------------------------------------
|/
---/---------------*---------*---------*---------*--------
/| | | | |
-/-|/\--------*---|-----*---|-----*---|-----*---|---------
| | | | | | | | | | |
|--|--|------|----|----|----|----|----|----|----|---------
\ | | |____|____|____|____|____|____|____|
--\|_/----------------------------------------------------
| __________
\| __________----------
p < __________ f
----------__________
Common dynamics markings include: