Update 6-11_schema.asciidoc

Small clarification of text.

Author: cloojure

06_databases/6-11_schema.asciidoc

@@ -157,10 +157,10 @@ can be related to--this means that entities can relate to themselves!
 
 You also use +:db/valueType :db.type/ref+ and lone +:db/ident+ values
 to model enumerations, such as the user roles that you defined. These
-enumerations are not actually schemas; they are normal entities with a
+enumerations are not actually attributes; they are normal entities with a
 single attribute, +:db/ident+. An entity's +:db/ident+ value serves as
 a shorthand for that entity; you may use this value in lieu of the
-entity's +:db/id+ value in transactions and queries.
+entity ID (the +:db/id+ value) in transactions and queries.
 
 Attributes with +:db/valueType :db.type/ref+ and +:db/unique+ values
 are implicitly indexed as though you had added +:db/index true+ to