The purpose of obtaining data is to prove or disprove a theory or hypothesis, which usually precedes the gathering of data. After the data has been collected it's analysed to see if it supports the theory or hypothesis. This process is called "interpreting the data".
Sometimes observation or an experiment appears to suggest that there might be a theory which explains the observed data. To test such a theory the data is closely examined to see if the theory fits the data. It may not exactly fit but it may be close. Interpreting the data is part of the process for deciding whether the theory is correct.
Performing many experiments or trials is often needed to test a theory or hypothesis thoroughly enough to draw conclusions, or perhaps to refine a theory or hypothesis. Once again, interpreting the data is an important part of this development process. Often an alternative theory suggests itself because it explains the empirical data (the actual results of experiment) better than some previous theory.