Document prefix not introducing a new route (#14318)

Author: markdalgleish

docs/api/framework-conventions/routes.ts.md

@@ -42,7 +42,7 @@ You can use the following helpers to create route config entries:
 - [`route`][route] — Helper function for creating a route config entry
 - [`index`][index] — Helper function for creating a route config entry for an index route
 - [`layout`][layout] — Helper function for creating a route config entry for a layout route
-- [`prefix`][prefix] — Helper function for adding a path prefix to a set of routes without needing to introduce a parent route file
+- [`prefix`][prefix] — Helper function for adding a path prefix to a set of routes without needing to introduce a parent route
 - [`relative`][relative] — Creates a set of route config helpers that resolve file paths relative to the given directory. Designed to support splitting route config into multiple files within different directories
 
 ### File-based Routing

docs/start/framework/routing.md

@@ -204,7 +204,7 @@ Note that index routes can't have children.
 
 ## Route Prefixes
 
-Using `prefix`, you can add a path prefix to a set of routes without needing to introduce a parent route file.
+Using `prefix`, you can add a path prefix to a set of routes without needing to introduce a parent route.
 
 ```tsx filename=app/routes.ts lines=[14]
 import {
@@ -230,6 +230,24 @@ export default [
 ] satisfies RouteConfig;
 ```
 
+Note that this does not introduce a new route into the route tree. Instead, it merely modifies the paths of its children.
+
+For example, these two sets of routes are equivalent:
+
+```ts filename=app/routes.ts
+// This usage of `prefix`...
+prefix("parent", [
+  route("child1", "./child1.tsx"),
+  route("child2", "./child2.tsx"),
+])
+
+// ...is equivalent to this:
+[
+  route("parent/child1", "./child1.tsx"),
+  route("parent/child2", "./child2.tsx"),
+]
+```
+
 ## Dynamic Segments
 
 If a path segment starts with `:` then it becomes a "dynamic segment". When the route matches the URL, the dynamic segment will be parsed from the URL and provided as `params` to other router APIs.