Content Repository

More generally, you would also need to buy or develop a Content Platform around the Content Repository to provide the features and services to support the syndication and multi-channel demands.

More generally, you would also need to buy or develop a Content Platform around the Content Repository to provide the features and services to support the syndication and multi-channel demands.

http://priocept.com/2011/08/16/content-management-vs-content-repositories-vs-content-platforms/

Sitecore.Services.Client provides a service layer on both the server and the client side of Sitecore applications to develop. This is completely configurable and extendable. Sitecore.Services.Client uses the ASP.NET Web API as a foundation.

What are advantages for Sitecore.Services.Client?

You can avoid writing server side code to access Sitecore items.

Sitecore.Services.Client provides two services:

ItemService

and EntityService

https://sitecorecontextitem.wordpress.com/2015/01/07/what-is-sitecore-services-client/

some of the functionality found in Sitecore.Services.Client seems to overlap with the functionality from the Sitecore Item Web API (Both allow you to perform basic CRUD operations on Sitecore items via web requests). While I do believe that there is some significant overlap between the two technologies, it is becoming clear to me that Sitecore.Services.Client offers a lot of new functionality that falls outside the scope of the Sitecore Item Web API.

The Sitecore Item Web API provides access to a REST-style web service that enables external applications to retrieve and manipulate Sitecore content via JSON output.

ItemService API reference

https://itemserviceapi.docs.apiary.io/#