Difference between data type designer and appian designer?

Appian Designer :
The Appian Designer is kind of workspace you can build a Appian application.
The default view in the Appian Designer is a list of all applications in the environment. From here, you can create or import new applications, modify applications, or drill into a single application to work on the objects associated with it. Drilling into an application brings you to the application designer, where they are presented with a list of the objects associated with the application.

You can see the Appian designer documentation from: docs.appian.com/.../welcome-app-designer.html

Data Type Designer:
The Appian Data type designer is used to define the business objects as part of the Appian application.
Here is the brief intro about the Appian Data type designer.
community.appian.com/.../appian-data-type-designer