You have created a task in the system, added participants and clicked on “In work” button. From that moment all the participants have your task in the lists. And the task text in their lists is in bold until they open the task form for the first time to get familiarized with it. Everything is like in e-mail.
But not exactly like that. If you click “Draft” button and then “In work” button again, everything will repeat. The task will again become unread for the participants. And they will again receive notifications to the e-mail if they are switched on. It is useful when you have changed the task text or attachments and want to report it.
If you look at any task panel in the list, on the bottom section of each task panel there is a transparent icon containing the number of responses. If one of the participants adds a new response, the icon with the number of responses in this task turns solid gray for other participants in their task lists.