Are session participants able to see each other?

If the session host wishes to allow meeting participants to enable their video, then, yes—session participants can see each other. This can be done in one of two ways:

1. Changing a "participant" to a "speaker." 
2. Granting broadcast permission to a participant. 

If you were in a session and did not want other participants to see each other, simply keep each person in "participant" status. They'll still be able to hear and see you but won't be able to see each other.