N(delta)-acetyl... vs N(alpha)-acetyl Can anyone tell me what  the difference between these two compounds is:

N(alpha)-acetyl-ornithine

N(delta)-acetyl-ornithine

The only difference I can think of is the chiral properties of the nitrogen atom, i.e. nitrogen inversion.

If that is the case, does it make sense to differ between these to compounds, or will they be constantly interconverted?
The difference does not lie in stereochemistry. Rather, N$^\alpha$-acetylornithine and N$^\delta$-acetylornithine are regioisomers of one another.

The superscript Greek letter denotes which nitrogen is substituted with an acetyl group. The lettering is relative to the carboxyl group as shown in the image below:



Note that:


The carboxyl group’s carbon does not get the $\alpha$, because it is considered part as the functional group from with the labelling begins
The $\alpha$ carbon is asymmetric. Both L- and D-compounds (or (S) and (R) according to CIP nomenclature) are possible for both N$^\alpha$- and N$^\delta$-acetylornithine.