What's the difference between "Request to Book" and "Request to Hold"?

Request to Book: You're ready to commit to purchasing this sponsorship opportunity; the Event Organizer will review your request and approve or reject. Note: If the request is approved, you will still have the opportunity to confirm your total purchase amount.

Request to Hold: You want to temporarily reserve the opportunity while you make a decision (holds are typically time-limited based on Event Organizer discretion). If a request to hold is approved, you will be able to convert the hold to a purchase when you’re ready, or release the hold if you no longer would like to purchase the opportunity.