Explanation/Reference:
Explanation:
You may want your workflow to collect information from the person who starts it, and then reference this information later in the workflow. For example, imagine that you are designing a workflow that assigns a document review task. In some workflows of this kind, it might make sense to always automatically assign the review task to the same participant and to always use the same formula for calculating the due date.
But in your workflow, you want the person who manually starts the workflow to specify both the reviewer and the due date. You can set this up by adding custom fields to the workflow initiation form and requiring that the workflow be started manually.

Reference: Create a workflow initiation form