Nobody wants to waste time, effort, and resources on a failed Master's or PhD application. For graduate school admission and funding, it may be beneficial to strategize your choice of schools based on the quality of the requirements that you have.
R1 universities are known to have very high research activities. They produce a lot of doctoral graduates, do some of the best research in the country and hence, they attract most of the research funds available. This can not be said of R2 universities which are sort of the opposite of R1 universities.
Free Course and Documents: Beating Competition for Grad School Admission and Funding in the USA.
In this video, I talked more about funding and which types of universities you may target if you have a low or high GPA.
You can find a list of R1 and R2 universities on this Wiki page.
Lastly, I must say that since R1 and R2 classifications are an aggregate measure of quality, it may be possible to have individual programs in R2 universities that are of comparable quality to those in some R1 universities.