---
source_url: https://www.pubnub.com/docs/chat/unreal-chat-sdk/learn/glossary
title: What's what
updated_at: 2026-05-22T11:04:46.094Z
---

> Documentation Index
> For a curated overview of PubNub documentation, see: https://www.pubnub.com/docs/llms.txt
> For the full list of all documentation pages, see: https://www.pubnub.com/docs/llms-full.txt


# What's what

We tried to keep Chat SDK simple and name things as they are. Still, certain terms might not be clear at first sight or are PubNub-specific. When in doubt, refer to this simple list.

| Term(s) | Description | Related docs |
| --- | --- | --- |
| **Channel** | A room created for at least two people to have a conversation. Channel members can send messages, receive messages, and react to them. You can also forward messages to other channels, quote, or pin them to the channel, and much more. What you can do on a given channel depends on its type and the permissions you have (granted or revoked through [Access Manager](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/users/permissions)). | [Channels](https://www.pubnub.com/docs/chat/unreal-chat-sdk/learn/chat-entities/channel) |
| **Direct** vs. **group** vs. **public** channel | Three types of [channels](https://www.pubnub.com/docs/chat/unreal-chat-sdk/learn/chat-entities/channel) you can create with the Unreal Chat SDK using three separate methods. The choice of a method/channel type depends on how many people you want to have in a given conversation. When you create a direct channel, you can invite only one person to a conversation when creating a channel, while group channels allow you to invite multiple members. Public channels, on the other hand, don't require invites. Anyone can join them as they are meant for larger audiences, like in virtual events. They also have certain limitations in place - you'll get errors when trying to implement such Unreal Chat SDK features as [typing indicator](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/typing-indicator), [invites](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/invite), or [read receipts](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/messages/read-receipts) in public channels since these features are neither useful nor practical for large audiences. | [Direct](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/create#create-direct-channel), [group](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/create#create-group-channel), and [public](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/create#create-public-channel) channels |
| **Connect** vs. **subscribe** vs. **join** | [Connecting](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/watch) to a channel lets you "watch" what is happening on that channel and see all new messages. This way, you become subscribed to this channel (or "present" on this channel) and receive all message-related events. To become a member of this channel, you must explicitly [join](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/join) it. In some cases, like a group channel, you can join a given channel only when [invited](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/invite) by another member of this channel or its admin (depending on the channel permissions). | [Watch](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/watch), [Invites](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/invite), [Membership](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/membership) |
| **Thread** vs. **channel** | The term `thread` or a `thread channel` refers to a `ThreadChannel` object, which is simply a channel created for a message in the main channel to keep the conversation related to one topic in one place. You can think of a thread as a "subchannel" of the main channel. Thread channels' IDs start with the `PUBNUB_INTERNAL_THREAD` prefix. | [Threads](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/messages/threads) |
| **Message** vs. **thread message** | A message that starts a thread is a regular `Message` object with the `hasThread` parameter set to `true` to distinguish it from other messages. All messages in a thread are called `thread messages` (`ThreadMessage` objects and their instances). | [Threads](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/messages/threads) |
| **Membership** | An object that describes a relation between a channel and a user and its status - whether a user [joined](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/join) a channel and became its member, or [left](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/leave) the channel. | [Membership](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/channels/membership) |
| **Message reaction** | You can perform various actions on a message (such as deleting or editing). When you add or remove an emoji to/from a message, you react to it, so you add/remove a message reaction. PubNub [Message Actions API](https://www.pubnub.com/docs/sdks/javascript/api-reference/message-actions) handles both cases. | [Reactions](https://www.pubnub.com/docs/chat/unreal-chat-sdk/build/features/messages/reactions) |