Updates to 'Database backends' page.

doc/db.rst

 Database backends
 =================
 
+The purpose of Flask-Admin is to help you manage your data. For this, it needs some database backend in order to be
+able to access that data in the first place. At present, there are four different backends for you to choose
+from, depending on which database you would like to use for your application.
+
 .. toctree::
    :maxdepth: 2
 
@@ -8,3 +12,16 @@ Database backends
    db_mongoengine
    db_peewee
    db_pymongo
+
+If you don't know where to start, but you're familiar with relational databases, then you should probably look at using
+`SQLAlchemy <http://www.sqlalchemy.org/>`_. It is a full-featured toolkit, with support for SQLite, PostgreSQL, MySQL,
+Oracle and MS-SQL amongst others. It really comes into its own once you have lots of data, and a fair amount of
+relations between your data models.
+
+If you're looking for something simpler, or your data models are reasonably self-contained, then
+`MongoEngine <http://mongoengine.org/>`_ could be a better option. It is a python wrapper around the popular
+*NoSQL* database called `MongoDB <http://www.mongodb.org/>`_.
+
+Of course, if you feel that there's an awesome database wrapper that is missing from the list above, we'd greatly
+appreciate it if you could write the plugin for it and submit it as a pull request.
+