Dynamic Fields is the place where you setup an manage custom fields for tickets and articles (see figure below).
Figure: The dynamic fields overview screen with some dynamic fields.
The dynamic fields configuration is described in more detail in the section "Dynamic Fields Configuration".
Each dynamic field type has its own configuration settings and therefore its own configuration screen.
Note
In the OTRS framework, dynamic fields can only be linked to tickets and articles by default, but they can be extended to other objects as well.