Rendering more than one independent page in the same layout, at the same time.
Parallel Routes — folders prefixed with @, like @analytics and @team — let a single layout render multiple independent pages simultaneously, each passed into that layout as a named prop (a 'slot'). This fits dashboards especially well, where different sections need to load, update, and navigate independently rather than being controlled by one page component.
Each slot behaves like its own mini route: it can have its own loading.tsx and error.tsx, and navigating within one slot doesn't affect the others. default.tsx defines what a slot renders when there's no route matching the current URL for that specific slot — necessary because every active slot has to resolve to something on any given navigation, even if that navigation only targeted one of them.
What you'll walk away knowing