Often, you’ll see shallow holes in concrete walls like this. Often they are patched up.
What are those for? I’m guessing it’s for curing the concrete, but it’s not clear to me how they’re used.
I think that they are marks from the forms. Probably something that allowed the forms to taken apart easily.
Holes from concrete form ties. The sheet metal panels that are used to make the walls could spread under the weight of wet concrete so metal ties are used to hold the sides together while the concrete sets. When the forms are stripped off, the ends of the ties are snapped off fairly flush with the concrete surface. If you could look into those little dimples in the photo, you would see the remains of the metal tie.
Yeah, I have noticed the metal remains. But then why isn’t flush with the concrete surface? Why the dimple?
Yep to post #3.
I believe that the ties are strategically “weakened” so that when they are broken off they are not flush or protrude from the outside of the wall. You wouldn’t want the jagged broken metal to jut out from the wall so they are engineered to break off a half-inch or so inside the finished wall.
In a perfect world, the concrete contractor AKA The Foundation Guy, uses his putty knife and a trowel and fills them all in with waterproof grout so they are perfectly smooth, watertight and invisible.
If you should find him, let me know. 
Well, often they’re left unplugged for aesthetic enhancements. It’s like that in my building, hence me asking this question. However the occasional place place they did fill them up (like in my apartment), they’re not even close to invisible.
It’s entirely possible that someone used that line as an explanation. It’s bullcrap. Trust me, someone saved a buck on the job by not filling the dimples.
As others have stated these are from the form ties.
Usually if they are left exposed like this it is intentional and part of the Architectural design. I have done several buildings with them exposed. But I think it is very difficult to pull this off–most of the time they never seem to line up the way I want them too!
If you don’t want them you can patch them, but then you have the issue of the concrete patch not matching the color of the original pour. Not a good look either.
Another type of finish you might see is board formed concrete—this is where they (originally) used actual boards for the formwork and the wood grain is left on the surface after the form is pulled. Nowadays this is usually done by a plastic shape put into the metal form–but in my opinion it looks fake and too repetitive.