Add data model intro paragraphs
Data Model
==========
-EdgeDB is a relational database with strongly typed schema.
+In this section you'll find an overview of the fundamental types, objects,
+and concepts for EdgeDB, a relational database with strongly typed schema.
+Here's a quick overview of the links below:
+
+Types in EdgeDB include your own **Object Types** (e.g. *User*) and
+**Abstract Types** for other types to extend (e.g. *HasEmailAddress* for
+*User* and others can inherit), plus **Scalar Types** with single values
+(str, int64, etc.) and **Collection Types** like **arrays** and **tuples**
+for multiple values.
+
+Start putting your **Object Types** together with **properties** and
+**links**. Then build on them with items like **annotations** (readable
+notes for others), **constraints** to set limits (e.g. maximum length,
+minimum value, or even create your own), **indexes** for faster querying,
+and **computables** to use expressions to define properties or links
+(e.g. *property email := .user_name ++ '@' ++ .provider_name*).
+
+**Expression Aliases** let you use existing types under new names to build
+on them without touching the original - both in your schema or on the fly
+inside a query. You can also create your own **functions**, strongly typed
+along with everything else in EdgeDB. All this goes into the schema under
+one or more **modules** (namespaces).
.. toctree::
@@ -25,4 +46,3 @@ EdgeDB is a relational database with strongly typed schema.
annotations
modules
databases
-
