The "owner" and "requestor" require email addresses. The "requestor" is the person who created the task and wants it completed. the "owner" is the person expected to complete the task. The task shows up in the To Do list of only the owner by default.
Type in a partial name or email address in the owner field, and Hiveminder will try to autocomplete the field with the people you've had contact with through Hiveminder. The special value "me" always means, well, you! You can also use the keyword "nobody" to deal with tasks with no owner, for instance.