Both waterfall and Iterative development methodologies follow the same SDLC stages like requirement gathering, design, development, testing, integration and deployment. It’s only that in iterative development these cycles repeat for every Iteration, but only once in waterfall same as how water falls from top to bottom.
That is, in Iterative methodology, the complex software product/project is broken into multiple Iterations. In each Iteration, all the stages of SDLC are followed. Business value functions are delivered in each Iteration. Where as in waterfall all the product features are implemented in one go.

Happy project planning...