The project design and functionality will need to be approved by the client. As progress is made, and the client is shown, the design may need to be altered. This process of involving the client at key points in the process and addressing the issues is considered the iterative process.
The goal of the process is to work in stages and perfect as we go along and avoid delay of the deadline as well as scope creep. Scope creep is defined as the initial set of goals being extended beyond the original intent. It is best to avoid this by setting an expectation that a certain number of designs that shall be created for review. The process to handle any design beyond that point would need to be accounted for in the original agreement.
Be aware that this back and forth, give and take iterative process only works well when both client and designer are responsible and provide feedback and changes in a timely manner. That is the only way to stay on track.