What is the difference between OpenERP and Odoo?

In OpenERP V7:

There have no any kind of website interface and E commerce faciality in this version so that the new territory comes in the market and new revolution for new API and also added new modules for Odoo 8.0

OpenERP V7 To Odoo 8.0

https://www.odoo.com/blog/odoo-news-5/post/odoo-8-release-notes-186

New Features for Odoo 8.0

http://www.nevprobusinesssolutions.com/top-12-odoo-8-features/

http://pragtechblog.blogspot.in/2014/04/openerp-8-features.html

For Odoo 9.0

By Febian Pianker

https://www.odoo.com/slides/slide/keynote-odoo-9-new-features-201

By netjunky

http://netjunky.net/odoo-9-new-features/

You can check for the above reference links to understand the OpenERP 7.0 To Odoo 8.0 To Odoo 9.0

I hope my answer may help you :)

You have the Release Notes of Odoo v8 in the oficial website with all the changes. And you can see what's new in these Odoo v9 videos