With 'Reproducibility' we mean that someone else (perhaps you in the future) can repeat the steps you performed and get the same result. See the Reproducible Research Task View.
To create reproducible results, all sources of variation need to be fixed. For instance, if a (pseudo)random number generator is used, the seed needs to be fixed if you want to recreate the same results. Another way to reduce variation is to combine text and computation in the same document.