Matlab array problem

Short story: i’m learning MATLAB cause university… I’m using the free resource given by Matlab himself… Right now they are saying the function “size” is used to determine the dimensions of an array (all understood) and to create an array with the size of another one (example: Rand(size(x))) (all understood again…. Problem: but while I was playing with this function I wrote “rand(size(2))” only to see what would happen and the MATLAB response