First of all, you need to add/invite a user to make him/her a Client. (Refer Image-1)

1. A client can create a project
2. A client can create a new task (and can assign a user)
3. A client can reply to a task
4. Can’t create a new user or add a user
5. A client can’t see the timelog for others (except his own)
6. Client won’t be able to view or create for the Invoice section, Gantt chart, Template and Daily catch-up
7. In Analytics (cant view the weekly usage and the resource utilization page)
8. No access to Company & Account Settings.

(Image-1)