Salesforce Object Query Language (SOQL) includes updates to the FOR REFERENCE and FOR VIEW.
REST API includes a new composite resource, SObject Collections. REST API composite resources improve your application’s performance by minimizing the number of round-trips between the client and server.
SOAP API includes new, changed, and deprecated calls.
Chatter REST API
Integrate mobile apps, intranet sites, and third-party web applications with Salesforce using Chatter REST API. You now can get up to 100 comments at a time, get lists of users who voted on posts or comments, and purge users’ Chatter-related activities.
Reports and Dashboards REST API
Reports and Dashboards REST API enhancements include new methods of report and dashboard folders, a URL parameter for the notifications resource to scope resources to Lightning dashboard subscriptions, new resources for report types, and new report and dashboard properties.
User Interface API
Build Salesforce UI for native mobile apps and custom web apps using the same API that Salesforce uses to build Lightning Experience and Salesforce for Android, iOS, and mobile web. Now you can get a directory of supported objects and build UI for picklists, dependent picklists, and lists.
Tooling API includes new and changed objects.
Metadata API includes new and changed types and fields.
Salesforce Console APIs