Dynamic fields are custom fields that can be added to a screen to enhance and add information to an object (e.g. a ticket or an article).
Tickets or articles could have as many fields as needed. It is also possible to use the dynamic fields framework for other objects rather than just ticket or article.
Due to its modular design each dynamic field type can be seen as a plug-in to a framework, and this plug-in can be an OTRS standard package to extend the available types of the dynamic fields or even to extend current dynamic field with more functions.