What is a push topic?

A push topic is a specific feature used within Salesforce that provides a mechanism for clients (usually external applications) to subscribe to real-time updates of records that meet certain criteria. This allows clients to receive notifications automatically when changes occur to relevant data.

By utilizing push topics, developers can define the criteria for the data they are interested in, and when records are created, updated, or deleted that match this criteria, a notification is sent to the subscribed clients. This real-time communication is particularly useful in scenarios where applications need to stay updated with the current state of data without having to continuously poll the server for changes.

Understanding that push topics facilitate subscriptions is key. In contrast, the other options describe different concepts within the Salesforce ecosystem that do not relate to real-time data updates. For instance, client requests refer to direct queries sent by clients to the server, while data validation concerns checks performed to ensure data integrity before it is saved in Salesforce. User permissions are about governing who can access or modify information within the system, distinct from the subscription mechanism of push topics.