Success in Sprints
Iterative action means that the development is split into phases. They usually last for 2–4 weeks. For each of these phases, the team plans anew, which elements shall be developed further. They do this by prioritizing the backlog. By assessing the effort for user stories, which are subtasks of a development phase, you can always estimate, which of the prioritized functions can be worked on in the next development cycle (sprint).
The current state will be delivered to you for testing after every iteration. This allows you to develop a feel for the product and to get to know the user experience, allowing you to take part in its design.