This depends on the VoiceBoxer configuration and which roles you are assigned to.
Single View: Only the active speaker can be seen and heard.
Speaker View: Multiple speakers can be seen on screen (active speaker + 5 panelists) but only the active speaker can be heard. The active speaker is placed in the main area off the screen.
Gallery View: Up to 13 speakers can be shown on screen but only the active speaker can be heard. The main speaker will still be highlighted in the top-left corner of the screen (top right if a presentation is uploaded)
Every participant in the Forum can be heard and seen (unless they mute themselves and turn off their camera). The Forum can obtain up to 13 participants and when you are not in the forum you won’t be heard or seen. If you want to join the forum you need to request the floor from the moderator.