Salesforce Object Query Language (SOQL) includes changes to limits and calls
Salesforce Object Search Language (SOSL) includes changes to limits.
REST API includes new, changed, and deprecated resources.
Chatter REST API
Integrate mobile apps, intranet sites, and third-party web applications with Salesforce using Chatter REST API. Personalization is generally available, and you can now get audience information for a batch of audiences. Search managed content in a community or channel. Increase view counts on knowledge articles.
Reports and Dashboards REST API
Reports and Dashboards REST API enhancements include new properties that describe subscription email attachments and report field to sObject relationships.
User Interface API
Work with new objects, access the record type ID for every record in a response, and get the case status in a picklist.
Tooling API includes new and changed objects.
Metadata API includes new and changed types and fields.