Types of Participants

There are four types of participants for workflow tasks. In the diagram on the Assignees subtab, each participant has an icon that tells you what type it is. If an icon is grayed out, that means the participant is disabled.

Single

The assignee is a single user or an application role. (Even though LDAP group is also a possibility, it's recommended that they're not used.) For example, the task is assigned to a user's manager, and the manager's approval is all that's needed for the request to go through. With application role, the task is routed to all users with the role, and someone can claim the task to work on it.

Parallel

A set of assignees must work in parallel, usually by voting. For example, the task is assigned to people who must vote to decide whether to hire someone or not.

Serial

A set of assignees must work in sequence, and the set is usually dynamic. For example, the task is routed up a supervisory chain for approval.

FYI

This is like the Single participant type, except that the assignees just get a notification and don't need to act on the task. In some cases, they can add comments or attachments, but they can't affect the outcome of the task.