Up in the R... is meant to help you find help on functions and statistical tests in R. Here you will find information on how to choose and run basic tests in statistics. You'll find examples and tips, and will be able to try these examples directly on your machine by copy-pasting the code into R. You'll thus be able to experiment with the code and get more confident writing or tuning it.
This section is certainly NOT meant to replace a proper course in statistics and you should not expect to systematically find all the reasons why tests may be used in specific cases or not. If you do not find what you want, you may check the section Useful links and tools and Useful books and docs at the bottom of each and every page on this website.
If you do not have any experience with R or if you still need to understand the basics of this language, you can start with R1 - introduction to R. Otherwise, move on to the next two modules.