fix to tenant definition in server_manager

chapter_4/server_manager.rst

@@ -16,7 +16,7 @@ Tenants
 ------------------
 
 This feature allows you to create or manage tenants.
-A tenant is typically a user who may or may not use specific product types or access some (or all) data sources within the same environment.
+A single Knowage instance can have one or more tenants. In case of a multi-tenant environment, each tenant owns and manages its own users, documents, configuration and parameters, which are completely independent from those owned by other tenants.
 The *Tenants* functionality is only available for the Knowage Enterprise Reporting (ER) license and users must have the superadmin role. 
 
 .. figure:: media/image61_8.1.png