Iterate is a verb meaning to say, do, or perform again. Iteration is a noun referring to an act or instance of iterating. It is synonymous with repetition, but iterations usually work toward a perfect form of something. In these sentences, for instance, iteration implies repetition:
The annual event, now in its 135th iteration, includes more than 2,500 animals across 179 breeds. [Salon]
The company will also launch the fifth iteration of its popular iPhone as rivals from Motorola Mobility to Samsung Electronics apply pressure. [Reuters]
Iterations help establish the cadence of work. [Forbes]
As the word logically only applies to repetitions, the first version of something can’t be an iteration. The second iteration of something would be the third version, the third iteration the fourth version, and so on—but few writers bother with this minor logical point.