There is a new Content Definition Menu Item in Orchard CMS 1.7 when you sign into the administrator dashboard. This menu item gives you access to Content Parts and Content Types in Orchard. Although a small change, this makes it easier for Orchard Developers and Site Administrators to keep certain roles from trying to access this information as well as makes it easier/faster to edit Content Types and Content Parts.
The Content Definition Menu Item is a new menu item just below Content on the admin dashboard. It allows power users and Orchard Developers to manage Content Parts and Content Types used in the Orchard Website. Most users shouldn't have permission to access this information as one wrong change can dramatically alter the information and stability in your Orchard Website. As a rule, make sure most roles and users do not have permissions to access this information.
Although the Content Definition Menu Item is new in Orchard 1.7, the functionality it provides is not. The Content Part and Content Type information used to be separate tabs when selecting the Content Menu Item. The information has been split out into separate menu items for two reasons. First, it makes it easier/faster to manage content types and content parts. Depending on what you're doing, this will save you a click or two to get to the Content Type or Content Part you want to manage.
Second, the new permissions that go along with this change make it easier to keep this information invisible to certain roles. By putting the Content Type and Content Part information in a separate menu item, Orchard Developers and Orchard Administrators can completely hide that menu item from users as appropriate. Most of the time you want various contributing roles to access the content, but you don't want them to alter the structure of the content.
Albeit the new Content Definition Menu Item is a small change in Orchard 1.7, but it makes it a lot easier/faster to manage Content Type and Content Parts as well as tighten down permissions to various groups who have access to the administrative dashboard. For more information on Orchard, check out my Orchard Tutorials and read these tutorials specifically on Orchard 1.7:
I have been developing Orchard Modules, Orchard Themes, and Orchard Websites full-time for 3 years as of this summer, so if you are looking for an Orchard Developer, please contact me!