One of the key concepts Ayn Rand describes is integration.
The purpose of integration is to build a logical structure of ideas into a whole. This means being consistent. Consistency is like a solid barrier, that’s very difficult for attackers to penetrate.
A building is the same: it’s a logical structure, not built on a foundation or sand or made so that it will collapse when the wolf huffs and puffs.
On a small scale, you might recognise the buttons and slider on a device, and notice that it needs to be plugged in to the wall to work.
However you don’t stop there and just accept this machine as shiny device with knobs and a slider that’s powered by electricity.
You consider it as a whole, and realise that the slider, knobs and so on work together for a purpose: to toast bread.
You recognise the machine as a toaster, even if your integration doesn’t expand into the opposite direction to include an understanding of how the electronics work, how power is created, and how electricity travels over distance to reach your toaster.
You have a broad general understanding—a conceptual understanding—that doesn’t conflict with your knowledge—however limited—of the toaster’s parts.
You don’t, for example, believe that just because the toaster has buttons and is powered by electricity, it will also blend your morning smoothie.
The key idea of integration, whether up into broad general concepts, or down into fine detail, is that ideas should complement, not contradict each other: that is, be logical and consistent.
This is why Ayn Rand developed her philosophy from the most basic philosophical axioms of existence, identity and consciousness to morality and then to what would make an appropriate social system.
She wanted to make all the parts of her thinking congruent with the whole. Not come up with some idea for society out of the blue that was inconsistent with her views of morality or existence itself.