A statistical hypothesis test is a method used in statistics. It helps you describe the results you get from an experiment. The hypothesis test tells you the likelihood that a specific result would happen by chance.
Statistical hypothesis tests answer the question: Assuming that the null hypothesis is true, what is the probability of getting a value which is at least as extreme as the value that was actually observed?.
So, for example, if the result would only happen by chance 5% of the time, then the experimental hypothesis is supported to the 95% level.