It's the language.

Colin Robertson · Colin Robertson · commit 04f618842ae5 · 2020-05-26T16:35:47.000-07:00
diff --git a/docs/cpp/toc.yml b/docs/cpp/toc.yml
@@ -1,4 +1,4 @@
-- name: C++ documentation
+- name: C++ language documentation
   href: ../cpp/index.yml
 - name: C++ language reference
   expanded: true

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-- name: C++ documentation`
	`1`	`+- name: C++ language documentation`
`2`	`2`	`href: ../cpp/index.yml`
`3`	`3`	`- name: C++ language reference`
`4`	`4`	`expanded: true`