> likened to a horizontal elevator, you step in through some doors, doors close, stuff happens, doors open, you step back out later and you're somewhere else.
I like this analogy.
> it doesn't just turn up periodically like an elevator
Aren't elevators summoned by a button and then have their destination set by different button? That seems very similar to tapping in an app to "come get me" and tapping again to "take me there".
It depends. In some tall shared buildings (the sort of place a company might rent a single floor because owning a building is eye-wateringly expensive and unnecessary) the elevators are intelligent and hooked to gate ID, so, if somebody arrives at the gate with an ID for floor 12, the next available elevator picks floor 12 and opens its doors. After all you're not allowed on the other floors so it's pretty obvious where you're going.
I like this analogy.
> it doesn't just turn up periodically like an elevator
Aren't elevators summoned by a button and then have their destination set by different button? That seems very similar to tapping in an app to "come get me" and tapping again to "take me there".