1-on-1 Chat Room is a chat room that consist of 1-on-1 chat between two users. This type of Chat Room allows you to have always same chat room between two users. Header of the room will be named by the pair's name. To create 1-on-1 Chat Room, you will need to know the opponent's userId.
When you want your many users to chat together in a single room, you need to create Group Chat Room. Basically Group Chat Room has the same concept as 1-on-1 Chat Room, but the difference is that Group Chat Room will target array of userId in a single method. The return of the function is ChatRoom object that you can store it in your persistent storage and then use it to enter the same room anytime you want.
At this moment, you can add up to 100 participants in a single Group Chat Room.
Channel is Chat Room which allows users to join without invitation. This will allow our clients to implement our SDK to create Forum, Live Chat in Video Streaming, or Public Channel like in Forum or Telegram.
At this moment, you can add up to 5000 participants in a single Channel.
You can read more on https://documentation.qiscus.com/chat-sdk-android/chat-room-types