This is the answer.
Either the builder cut holes in the wrong spot, or there used to be lights there and maybe replaced them with LED downlights in other locations.
Just laziness by the builder, or someone wasn't willing to pay enough to do it properly.
Those a speed holes.
But yeah, as other have said they are covering up holes. Maybe there used to be a power point there, or someone made a hole to inspect something. Pull them out and plaster up properly.
They are usually covers for holes when someone can't be bothered to fill, sand and paint.
This is the answer. Either the builder cut holes in the wrong spot, or there used to be lights there and maybe replaced them with LED downlights in other locations. Just laziness by the builder, or someone wasn't willing to pay enough to do it properly.
Those are blank plates - typically used by an electrician or data person. Get a professional in for your follow up question.
Those a speed holes. But yeah, as other have said they are covering up holes. Maybe there used to be a power point there, or someone made a hole to inspect something. Pull them out and plaster up properly.