Within your yap inbox, (found by clicking the Yaps tab,) you should see a mixture of 1:1 (private chat between 2 users) and group yaps (group conversations with multiple users, made either by location/role or by adding individual users).
What are they?
1:1 yaps
Grey emoticon next to the conversation title;
Conversation title is the name of the individual you're chatting to in the conversation;
Conversation icon is the profile picture of the individual you're chatting to in the conversation.
Group yaps
dedicated conversation title;
administrator and participants list visible by clicking the (i) icon in the top right corner of the yap.
This group yap could be made up of roles and locations or individuals. If the chat is made using groups, this will automatically update the chat participants, as users move in and out of that group, reducing admin for the chat owners and administrators
To see a complete list of users currently in a group chat, click any message and select "Who has read this message?" on the context menu. The list of those who have and have not read the message contains all conversation participants.