What is the name of subject for testing which distribution the set of data follows?
I become frustrated since I am a beginner in this area.
What is the name of subject for testing which distribution the set of data follows?
I become frustrated since I am a beginner in this area.
This would fall under hypothesis testing. You hypothesize a distribution and test whether it is plausible that the data follows that distribution.
In most situations, you can't find out which distribution a set of data has been drawn from; you can sometimes be quite confident that it hasn't been drawn from some distributions (e.g. if it's clearly bimodal, you might be able to be pretty sure it won't be a random sample from a unimodal distribution).
So if you're testing whether your data come from a specific distribution, say a normal distribution (using something such as a Shapiro-Wilk test), then a rejection might lead you to be confident that your data are not drawn at random from a normal population -- but a failure to reject doesn't imply the data are drawn from a normal population, only that you didn't have a large enough sample to detect deviations from it.
There are some tests for a specific null hypothesis (i.e. with all parameters specified, such as the Kolmogorov-Smirnov, or the Anderson-Darling), and there are other tests for a specific distributional form but with some parameters unspecified (e.g. the Shapiro-Wilk test for normality).
This kind of testing is called goodness of fit testing.
There are many posts on site about this. One that it might be worth starting with is Is normality testing 'essentially useless'?