The current Pega 7 Fundamentals course exercises were designed to work with the multi-tenancy cloud exercise environment provided with self-study course enrollment. That exercise environment is staged on Pega 7.1.6 (v7ml6) with an additional Pega Academy RuleSet and staged rules. If your version of Pega 7 personal edition is not 7.1.6, there will be differences and some of them may be considerable due to the missing staged RuleSet.
In 7.1.7, the term "Data Types" references the same thing as the 7.1.6, "Data Object Types." Every ML release of Pega 7 has some slight product evolution toward simplification and therefore I would suggest that you use the online exercise system intended for the Pega Fundamentals course and not Personal Edition 7.1.7. After you have a fundamental understanding of Pega 7 (the Fundamentals course is built in 7.1.6) they you can research "What's New in Pega 7.1.7." after the fact.
The answer to your question related to the difference may be found in Pega 7 Developer Help (also available on the PDN). Specifically, Pega Developer Help for version 7.1.7 states,
"Creating new data types and data pages
To create new data object types and data pages, click the Create option on the menu bar and select what you want to create.
When you select "Add/remove data types", a process appears that lets you quickly add data types to the current application from another application, create a new data type for the application, or remove one you have previously added. See Add/Remove data types."
To get this answer, I went to the PDN (pdn.pega.com) and under the Resources topic chose Help for Pega 7.1.7.
You'll immediately notice the landing page for Pega 7.1.7 Help is titled "What's New in Pega 7.1.7," Every new release of Pega 7 has a "What's New" landing page.
You're query is specifically about a Designer Studio feature though, so I clicked Designer Studio under the Contents tab on the left. This results in displaying the Designer Studio basics landing page on the right. Scrolling down, under the Data subtopic in the Explorer area section on the right, I clicked filter the results. This resulted in the landing page titled "About the Data Explorer" and that's where I found the Pega 7.1.7 definition.
Please note that Pega Academy does not yet have any formal courses built on Pega 7.1.7, but Pega 7.1.6 is not terribly different, but I'd still recommend you use the online exercise system devoted for the Pega 7 Fundamentals course and not Pega 7.1.7 Personal Edition. Features will exist in that newer edition that are not documented in the Pega 7 Fundamentals course as the course materials are designed for use in the online exercise system only (7.1.6).
Thank you for your understanding. I've pasted an image of the above mentioned landing page below.