Final answer:
The two core services of the Sitecore Services Client are the Item Service and the Entity Service, both facilitating different aspects of data management and interaction.
Step-by-step explanation:
The two core services that make up the Sitecore Services Client are the Item Service and the Entity Service. The Item Service provides a RESTful API that allows developers to interact with the Sitecore content tree, performing operations such as creating, reading, updating, and deleting content items. On the other hand, the Entity Service provides a mechanism for working with data entities that are not necessarily part of the Sitecore content tree, thus allowing for a more flexible data management approach.