How icon packs work
Discord refers to each icon by name and resolves it to a bundled asset. An icon pack hooks that resolution: for every icon name it provides a replacement for, Unbound redirects the asset to your image instead of Discord’s. Names you don’t override fall through to Discord’s originals, so a pack can be as small as a handful of icons or as complete as you like. Internally each overridden asset carries aniconPackPath (where your replacement image lives) and an iconPackScale (the density it’s authored at), which is how Unbound resolves your image at the right resolution.
An icon pack overrides icons by name. The same asset names the assets module discovers are the ones you target, so the naming you see there is the naming a pack overrides.
What an icon pack ships
Manifest
Metadata identifying the pack: name, authors, version.
Assets
How Discord’s icons are named and discovered: the names a pack overrides.