The input type From other workflow, means that this workflow can only be called from another workflow. This is normally referred to as a sub-workflow.
Examples of use:
A sub-workflow can be called from multiple main workflows, so you can use this to re-use the same subset of workflow elements.
You can also refer to a sub-workflow as an error workflow - i.e. a workflow to be called if an error should occur.
You can use a sub-workflow to group workflow components together which can be the complete workflow more transparent.
The output of the main workflow must fit the input type of the workflow defined in this manner.
This workflow input type has these settings:

- Endpoint unique ID
Here you state a unique ID for the current workflow. The other workflows, that are to call this workflow, will refer to the workflow by this name. - Input type
The type of input, that the main workflow should have as payload, when calling this workflow.
Possible values are:

- Sample XML file
If you are going to do conditions and/or Xpath expressions, then it is recommended to refer to an optional, sample XML file. If you click the magnifying glass, then you can select the sample XML file, that you want to use as a reference. - On error workflow
Another workflow to be called, if there is an error during processing of this workflow. This can be overwritten with another workflow.
If you want to call such a sub-workflow, then you can click the '+' icon and then see the list of possible workflows via the Workflow tab:
The dark grey elements are workflow groups, which can be expanded in order to see the workflow within this group.