question's in the title - pretty simple I guess.. what does this mean? and also 'In each ring describe the units and non-zero elements.'
Many Thanks
first, it must be a ring, then, the multiplication operator is commutative and lastly, it contains (an element) the unity 1 which has a property that for any element $\displaystyle r$ in the ring, $\displaystyle r\cdot 1 = r = 1\cdot r$