What is the purpose of calculating a test statistic? how does this value describe how the sample data either supports or contradicts a claim?

The purpose of calculating a test statistic is to know the performance of a certain data to be studied. By comparing and contrasting it using data analysis and methods. From the analysis, one can visibly support or reject the data if it gives the desired answer. That way, no one can contradict what the data says about the results since it is just base on the samples collected.