When you preregister your research, you're simply specifying to your plan in advance, before you gather data. Preregistration separates hypothesis-generating  (exploratory) from hypothesis-testing (confirmatory) research. Both are important. But the same data cannot be used to generate and test a hypothesis, which can happen unintentionally and reduce the credibility of your results. Addressing this problem through planning improves the quality and transparency of your research, helping others who may wish to build on it.