Restore intro section

Per Tener and r0mant feedback, integrate the introduction from the
Database Access Controls page into the newly merged RBAC guide. Frame
Database Access Controls as encompassing both databases and database
objects.

docs/pages/database-access/rbac.mdx

@@ -1,18 +1,35 @@
 ---
-title: Database Access RBAC
+title: Database Access Controls
 description: Role-based access control (RBAC) for Teleport database access.
 ---
 
-Role-based access control (or RBAC, for short) allows administrators to set up
-granular access policies for databases connected to Teleport.
+**Database Access Controls** is a Teleport feature that lets you configure
+role-based access controls for databases and the data within them. With Database
+Access Controls, you can ensure that users only have permissions to manage the
+data they need.
 
-An example of a policy could be, *"database administrators have access to
-everything, QA team and engineers have full access to staging databases, and
-engineers can gain temporary access to the production database in case of
-emergency"*.
+Access Controls encompasses two levels of granularity:
 
-For a more general description of Teleport roles and examples see [RBAC](../access-controls/introduction.mdx), as
-this section focuses on configuring RBAC for database access.
+- **Databases:** databases enrolled with your Teleport cluster.
+- **Database objects:** tables, views, or stored
+  procedures. 
+
+For both databases and database objects, Database Access Controls grants or
+denies access based on Teleport labels. When you enroll a database with
+Teleport, you can configure the labels associated with the databse. For database
+objects, you can define import rules that instruct the Teleport Database Service
+to apply labels to database objects imported from databases that match labels
+configured within the import rule.
+
+When a user connects to a database, the Database Service selectively grants
+permissions by checking labels against the user's Teleport roles.
+
+The Database Service grants object-level permissions for the duration of a
+connection and revokes them automatically when the connection ends.
+
+For a more general description of Teleport roles and examples see
+[RBAC](../access-controls/introduction.mdx), as this section focuses on
+configuring RBAC for database access.
 
 ## Role configuration