Presence detection refers to the process of tracking the online or offline status of users and devices, which is essential for applications like chat rooms, multiplayer gaming, and sensor networks. The tutorial outlines a straightforward six-step method to integrate presence functionality into applications using PubNub API by installing the API, inputting publish/subscribe keys, subscribing with presence events, unsubscribing, and detecting users in the channel. Additionally, the tutorial highlights other PubNub core features such as Pub/Sub Messaging for various apps, Storage & Playback for message retrieval, and Access Manager for controlling data stream permissions, along with extra resources for implementing presence detection across different platforms like JavaScript, PHP, and IoT devices.