an open house is organized by a real estate agent who want to show a certain house to the ones who are interested. this type of sale is similar to the one in which people go from door to door to sell their products. in this case the real estate agent opens the door to the house he wants to sell to potential buyers. instead of meeting with people to show them houses they sit in the house and wait for people to come in and take a look at it. if you plan ahead your open house you increase your chances of finding a buyer for your house.
the purpose 