Hello friend, UR means unreserved, the category which is not taking advantage of any type of reservation. As reserved category includes SC, ST, OBC and Physically Handicapped candidates. Some of the General Category students are also Handicapped, therefore the candidates who are not taking the advantage of any type of reservation are categorized in UR i.e. UnReserved category.  If you have any further query please let me know in the comments below.