Clarifying purpose of index

Author: ycombinator

docs/en/stack/security/authorization/built-in-roles.asciidoc

@@ -51,7 +51,8 @@ NOTE: This role does not provide access to the logstash indices and is not
 suitable for use within a Logstash pipeline.
 
 [[built-in-roles-beats-admin]] `beats_admin` ::
-Grants access to the `.management-beats` index for managing configurations.
+Grants access to the `.management-beats` index, which contains configuration
+information for the Beats.
 
 [[built-in-roles-beats-system]] `beats_system` ::
 Grants access necessary for the Beats system user to send system-level data