What is the difference between native and cross-platform apps?

The difference is where the interface is drawn and how the platform is reached. Native code calls the platform's own toolkit directly. A cross-platform app draws its own interface and reaches native capabilities through plugins — thin bridges to platform code. For the common capabilities, camera, location, notifications, storage, well-maintained plugins already exist and you never see the bridge.

Where it stops being seamless is a capability with no maintained plugin — a specific piece of hardware, or a vendor SDK that only ships native. Then someone writes that bridge, and the cross-platform saving on that feature disappears. You also still need platform knowledge for signing, permissions and store review regardless, so cross-platform reduces the duplicated work rather than removing one ecosystem.