In chemistry, dynamics is a field closely related to kinetics. Most textbooks cover both topics simultaneously, with the exception of most organic chemistry textbooks.

The difference is that while kinetics deals with the mathematics of reactions, dynamics deals with the actual mechanisms involved.

An example from organic chemistry:
Kinetics tells you an SN1 reaction occurs at a rate proportional to the concentration of one reagent, and independent of the other reagent's concentration.
Dynamics tells you that the product of the reaction will be a racemic mixture rather than one specific enantiomer since the carbocation has two sides open to nucleophilic attack.

Basically, kinetics is quantitative while dynamics is qualitative.

The study of dynamics helps chemists know which types of structures are the most or least reactive with other molecules. This helps decide what the best reagents are for producing a given product, and which reagents (and solvents) to avoid.