These are individual calls where only you and the person you are calling will be able to hear each other.
Individual calls are unlimited for everyone using BiPTT.
Channel calls (group)
Create groups (channels) with unlimited number of participants, where:
All users on the channel will be able to hear all incoming calls;
Outgoing calls will be received by everyone.
The number of channels is unlimited in the Pro plan and you can have 1 channel for up to 5 people in the free use of the app.