Iterative Development

Iterative development is the centrepiece of the Principles of Agile Manifesto:

Deliver working software frequently, from a couple of weeks to a couple of months, with a preference for a shorter timescale.

It is the antithesis of the hypothetic "Waterfall" methodology, which aims to deliver a project in a cascading, finite work stream, with results delivered at the end.

In the book The Art of Game Design, the importance of iterative development is summarised in this quote from Rule of Loop:

"The more times you test and improve your design, the better your game will be."