If you are a member of a space, and your administrator has given permission, you can mute/unmute other particpants audio or start/stop their video feed.
Select a participant from the particpant list or click the participant's video to access a dropdown that lets you turn audio/video feed on or off.
You can also mute everyone except yourself if you click Participants above the list of participants. This is useful if you are hosting a webinar or teaching a class. You can always unmute individual particpants as needed.