The ModelBuilder toolbox provides a varied collection of tools that support building models and are intended for use only in ModelBuilder and not in Python scripting.
In ModelBuilder, you can iterate the entire model or an individual process using tools in the Iterators toolset. In addition to the iterator tools, ModelBuilder has a set of supporting tools called Model Only tools.
The Iterators toolset has twelve iterators that help repeat a process or set of processes on a set of inputs.
The Model Only Tools toolset contains tools that are only used in ModelBuilder. Some of the tools are used to control the flow of processing while others are simple support utilities.