A UDim2, which is basically two UDims (Universal Dimenstions) being represented within the same object, is a Lua object which stores information about the size and position of GUI elements. The difference between a UDim and UDim2 is that a UDim2 represents a two dimensional plane with x and y coordinates while a UDim only accounts for one coordinate. The constructor takes parameters in the order: xscale, xoffset, yscale, yoffset.