Review#6: incorporate docs review suggestions.

docs/user/security/session-management.asciidoc

@@ -2,21 +2,19 @@
 [[xpack-security-session-management]]
 === Session management
 
-When you log in to {kib} it creates a session that is used to authenticate any subsequent request to {kib} made on your behalf. {kib} encrypts any sensitive session information and stores it in a dedicated hidden {es} index. By default, the name of that index is `.kibana_security_session_1` where the prefix depends on the name of the main `.kibana` index.
+When you log in to {kib} it creates a session that is used to authenticate subsequent requests to {kib}. A session consists of two components: an encrypted cookie that is stored in your browser, and an encrypted document in a dedicated {es} hidden index. By default, the name of that index is `.kibana_security_session_1` where the prefix is derived from {kib}'s primary `.kibana` index.
 
-Additionally, for every new session {kib} creates an encrypted client side cookie that is stored in your browser and sent to {kib} with every request. This way {kib} can associate request with the session information stored in the session index.
-
-When your session expires, or you log out of {kib} explicitly it will invalidate your cookie and remove session information from the index. In addition to that {kib} performs a regular session index cleanup to remove any expired sessions that weren't invalidated explicitly.
+When your session expires, or you log out of {kib} explicitly it will invalidate your cookie and remove session information from the index. {kib} also periodically invalidates and removes any expired sessions that weren't invalidated explicitly.
 
 [[session-idle-timeout]]
 ==== Session idle timeout
 
-You can configure timeout to expire idle sessions. By default, a session stays
+You can optionally expire sessions after a period of inactivity. By default, a session stays
 active until the browser is closed. To define a sliding session expiration, set
 the `xpack.security.session.idleTimeout` property in the `kibana.yml`
 configuration file. The idle timeout is formatted as a duration of
 `<count>[ms|s|m|h|d|w|M|Y]` (e.g. '70ms', '5s', '3d', '1Y'). For example, set
-the idle timeout to expire idle sessions after 10 minutes:
+the idle timeout to expire idle sessions after 10 minutes of inactivity:
 
 --
 [source,yaml]