What is the difference between a Host and a Co-host and an Alternative Host in Zoom? 
Host controls allow you as the host to control various aspects of a Zoom meeting, such as managing the participants. 
The co-host feature allows the host to share hosting privileges with another user, allowing the co-host to manage the administrative side of the meeting, such as managing participants or starting/stopping the recording.  
The host must assign a co-host and this must be done once the meeting has started.  
There is no limitation on the number of co-hosts you can have in a meeting or webinar. 
Co-hosts do not have access to the following controls as they are only available as host controls in a meeting: 
Start closed captioning and assign someone or a third-party to provide closed captioning 
End meeting for all participants 
Make another participant a co-host 
Start waiting room (co-hosts can place participants in waiting room or admit/remove participants from the waiting room) 
Start a meeting. If a host needs someone else to be able to start the meeting, they can assign an alternative host.  
Co-hosts cannot create Polls. They can administer them but not create them. 
The difference between a host and a co-host and a participant: