The P value, or calculated probability, is the probability of finding the observed, or more extreme, results when the null hypothesis (H0) of a study question is true – the definition of 'extreme' depends on how the hypothesis is being tested.
When a data scientist run many tests in this way, it's called p-hacking or dredging and it's a serious methodological issue. P-hacking results in spurious correlations instead of generalizable results.