Most hotels will allow you to provisionally book facilities and rooms at their property while you organise all of the delegates. This is one of the most difficult stages of organising an event. You have to liaise with people and suppliers to find one date where everyone is available. Sometimes you will need to reserve more than one date so that you can eventually choose the best one when you have jumped through all the hoops.
Reserving a hotel's facilities in an open ended agreement would cause problems for the hotel, so the options system has been created to try to meet everyones needs.
If you provisionally hold dates that are available then you will be given a first option. The hotel will hold this while you get yourself organised. If someone else wants the same dates then they will be given a second option. The hotel will then contact the first option holder and give them a time limit, which may be a few days. If they cannot confirm the booking then they may lose the dates, or they may find themselves holding the second option which gives the other client a chance to confirm.
In some cities, or at popular times of the year, or at popular venues, you may find yourself offered a third option. This may sound terrible, but the hotel conference department will contact the other clients and you may find yourself moving very quickly to second option and then up to first. It is worth taking control of the situation. For example you might say to the venue; 'You are our first choice but we need to give you a deadline so we can look at other venues'. A sense of urgency always helps.
This may seem a complicated way of doing business, but it does actualy work fairly well. It gives organisers a chance to get their event in order and it protects hotels from having rooms booked out which do not confirm. If you have any concerns about it then you can work with a conference organiser and they will take care of it for you. Conference organisers earn commission from hotels, so they can take the work off your shoulders without adding to your costs.