No worries, it's just a generic question that applies to more than just the Integra.
I'll stop farting around and actually answer it. h:

N/A stands for naturally aspirated. That term, applied to engine tuning describes a specific method that does not rely upon any form of intake pressurization (i.e., supercharger or turbocharger) to increase power.

N/A motors rely upon high compression and optimized cams, heads and manifolds to maximize engine efficiency and therefore, specific output.

In the case of Honda motors specifically, the combination of excellent OEM head design and the flexibility of the secondary VTEC cam lobe grant significant room for improvement.