Presence tracking in applications, facilitated by PubNub's Presence API, is crucial for managing connected users or devices in real-time across various domains, such as telemedicine, logistics, chat, and IoT systems. It involves monitoring user or device activity, triggering events when they come online, go offline, or time out, and updating systems accordingly to ensure operational efficiency and accurate data logging. Presence events, including join, leave, and timeout, are essential for maintaining user occupancy records and can be managed using webhooks that allow developers to execute logic both within the PubNub environment and externally. This functionality is particularly beneficial in chat applications for tracking user availability and in IoT systems for monitoring device connectivity, offering a reliable way to integrate user activity data into broader application ecosystems. Setting up Presence involves enabling the feature within the PubNub admin portal, configuring webhooks with callback URLs, and building event handlers to process and respond to these events, ensuring seamless integration and robust user activity management.