Project is a place to plan and discuss your engineer approaches, collaborate to colleagues, track the tasks, share file links for materials and results.
Private projects are visible only for members.
Public projects are visible for everyone (for anonymous visitors too).
Project admin can switch project Private flag at any time.
List of users in your project team. You (or another project admin) can invite users to join with Add member button. User got notification and could accept your invite.
Admin can create product list. Project members can add products to list.
This useful to get the quick access to products, related to your project. For example, this can be a list of existing products, modified in your design.
Admin can create and edit project milestones. Milestone can contain only text title, or plan and fact date.
Task is a way to organize your work, describe the goals, assign task to project members (or to yourself). Task can be linked with another tasks and targeted to milestones.