Tasks are great for setting reminders for what needs to be done and when it needs to be done by.
From within a project you can assign tasks to yourself or other project members. A task could be as simple as sending an email. It's completely up to you how you use them.
Your project activity feed and your project members' will be populated as you make use of your projects.
Uploading media, adding comments, etc will be logged in your activity feed.
This is a great way to quickly catch up with everything new that's happened since you last visited the site.
Your progress feed keeps you up to date with the projects and magazines that you're following.
Whenever they post a progress update, or update their cover page, you'll find out about it here. You can also comment on these updates.