They are both similar and their end results are almost the same. An alternative host is someone who you can allow to start your meetings on your behalf. If you know you are going to be running late to a meeting, you can make a licensed user in the same account you are in, an alternative host for the meeting. When you set them as an alternative host, it will send them an email allowing them to start the meeting. When they start it, they become the host and when you join you would become a co-host. A co-host itself can only be assigned during a meeting.

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