Conceptual Alignment

So, fundamentally, Conceptual Alignment, also known as Celestial affinity, is about what one's Mind-Soul Interface is adapted for. Transmutation of Will is a lot more efficient with regards to such physical substances.
People are made of biological matter: flesh, bone, blood etc. So that's what the mind-side of their MSI is primarily tuned to: biological mechanisms and synapses. Similar deal for Ghouls.
This is where extensional Arcanism (i.e. literally everything that isn't hard light) becomes efficient. Take Xiphaem Circuits: it works because it's basically the act of claiming blood as one's own, and using the soul to manipulate it. This is efficient because the MSI is already tuned to accept blood and other biological matter as part of oneself, so adding some more isn't that much of a stretch.
Take someone Bloodless like Murmur. They simply don't have that biological MSI, and consequently don't get that massive efficiency boost. Murmur in particular, however, has a conceptual alignment to water due to having subsumed the soul of a kraken, and have their own unique medium to work with as a result.
Amaryllis of Whitewood is another example of an unusual conceptual alignment- one towards glass. The ability to manipulate this material with unheard of efficiency earned her the moniker of "Crystal Dragon", among others.
But in things that aren't human, you've got different MSI adaptations according to their relevant Patterns of Life. People with high chaotic affinities also generally get Celestial affinities to the corresponding elements- midland nobles and their fire manipulation is an example of this. The Cotd affinity for solid shadow is a big part of what makes Sorcery hard to learn for non-Cotd.