Examples of the additive identity
$ 3 + \red 0 = 3 \\ a + \red 0 = a \\ \frac 1 2 + \red 0 = \frac 1 2 \\ -\frac 1 2 + \red 0 = - \frac 1 2 $
The additive identity is a good name for this property because it is a special property of addition.
Ask yourself, what can I add to any integer or real number, which we'll call 'a', whose sum is 'a'. The answer is zero.
The addditive identity : Any number plus zero equals the original number.
$ 3 + \red 0 = 3 \\ a + \red 0 = a \\ \frac 1 2 + \red 0 = \frac 1 2 \\ -\frac 1 2 + \red 0 = - \frac 1 2 $