ConnectApi is the Apex namespace that includes Chatter in Apex functionality.

Any questions about the methods in the ConnectApi Apex namespace should have the connect-api tag. The ConnectApi classes and methods are referred to as "Chatter in Apex" and contain most of the functionality offered in the Chatter REST API. A primary use case is to create customized Chatter UIs in VisualForce.

In the Apex documentation, you'll find information about Chatter in Apex in two main places:

Working with Chatter in Apex

ConnectApi Namespace reference

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