What don't you understand? The R just stands of the relation, the N represents the set of natural numbers, and mRn just means (I believe) that m is related to n, or (m,n) is an element of R.
To solve the question, take the 3 properties of an equivalence relation and compare them to R and see if all of them work out or (at least) one of them fails. If a requirement fails then provide an example, then you are done. If none of them fail, then prove mathematically how they all work out from the original description of R.