This is usually caused by improper compaction. Minor voids are usually cosmetic and can be surface patched. If this void is structural, it should be assessed and properly fixed.

if this is limited to the area in the photo, the only concern is aesthetics.

Thank you. How do they usually address these?

Concrete piers along foundation walls are considered structural. They maintain the stability and integrity of the foundation wall, etc., and prevent foundation failure; some are used to support girders that carry building loads.

If you want to address this, you should contact the person who prepared the drawings and designed the foundation or contact an independent engineer; they usually charge a fair price to come out and evaluate the issue, and they charge a little more if you want it in writing.

It's like buying a 1st car for your kid, you take it to a mechanic, and you pay $100-200 to check it out, make it safe :)

If it is addressed at all, maybe a little cement patch or parge the wall. Not really a concern unless structural as mentioned by @GN Builders L.L.C.

Plastcizers and super plasticizers and/or vibration are used to reduce voids and honeycombing in concrete. Here the worker in the foreground is pouring the concrete. The other two are operating a vibrator. I speced the vibrator and the foundation contractor added the chemical.

(I've had other forming contractors who acted like they never heard of such a thing. I stopped one job with several mix trucks lined up till I found and rented a vibrator and a generator to run it! )