Dynamics is the volume at which you play.
An excellent overview of dynamics marks can be found in the book Band Expressions (link).
A good introductory video on dynamics (link).
There are eight dynamic levels. Listed here are from loudest to softest:
In addition, there are two terms for gradually increasing/decreasing the dynamics:
There are also two markings for accents, which mean that the note is played louder than the surrounding ones.
= accent
Here are some tips on how to additionally affect the dynamics.
One of the main ways to control dynamics with a drumset is adjusting the stick height when striking a drum / cymbal.
Another is the location at which the stick hits the drum head. The dynamic level decreases as the sticks move towards the upper end of the drum.
Use lighter sticks.
Use brushes.
Use rim click.
Play cymbals with the tip of the stick, not the shoulder.
For light crashes and effects, hit the cymbal with the edge of the stick while holding a stick at a 90-degree angle to the cymbal edge.
Keep the foot down when playing hi-hat and bass drum.
Do not open the hats more than 1/4 of an inch.
Use heavier sticks.
Use sticks with nylon head.
Use the stick shoulder to hit the drum/cymbal.
Use the stick shaft (the flat part) on hi-hat for extreme sound volumes.
Use your full arm.
Use rim-shots on drums.
Turn the sticks around and play with the butt end.
Play the pedals with the feet up.
etc.
Fluidity is closely related to dynamics but involves fluid movement across the kit as well within a dynamic range. See link below.