Add an access control groups section

src/pages/how-to/routing-traffic-to-private-networks.mdx

@@ -93,6 +93,17 @@ Distribution groups define that peers that belong to these groups set in this fi
     It doesn't remove the need for the routing peer to be connected to these peers
 </Note>
 
+### Access Control Groups
+These groups provide granular control over internal services within your network. They are used as the destination
+groups in access control policies, allowing you to precisely define which internal services can be accessed by
+different network entities.
+
+When you associate these groups with specific routes, the routes will inherit the access control policies where
+the groups are defined as part of destination groups. This setup enforces access restrictions based on the policies,
+ensuring that only authorized traffic can reach the designated services.
+
+Routes that do not incorporate these groups will permit unrestricted access, allowing all traffic to pass through
+without any limitations.
 
 ## Managing network routes
 A network route describes a network you want to connect with your NetBird peers. It has an identifier, a network range, a routing peer or set of peer groups, and some parameters available for managing priority and masquerading.