Every room type needs a price. There is possibility to alter the price according to number of guests in the rooms, but it's not mandatory. Prices are based on seasons. In case you have fixed prices all along the year, you just need one season (default). In case you alter prices according to the high and low season, just click on 'create new season' and change prices. If you omit room, system will use price from default season.
If you offer any additional fixed services, this is the place to add them. Best example would be a breakfast. You set the price and guests can decided whether they are interested. The price will be added to the overall price of the reservation. Please note there are two types of extras. One is based on room per day and the other on person per day.