Booking request: By default, when you book an Eatwith experience you will usually be making a booking request - which means that you will need to wait for your host to accept and validate your request. Once they have done this, you will receive a confirmation email with the host's address and contact details. The booking button says "Request a booking".
Instant booking: An instant booking means that you can make a booking without having to wait for approval or validation by the host! You can see if an experience is instantly bookable if the booking button says "Book now" and there is the little lightning bolt, as per the photo below: