An open house is a set block of time, usually a weekend afternoon, when a home that is for sale is open for buyers to walk through without booking a private showing. The listing agent or a hosting agent is present to greet visitors, answer questions, and capture contact details from the people who attend.
For the agent, the value of an open house is rarely the immediate sale of that specific home. It is the pipeline: the buyers, and sometimes future sellers, who walk through and can become clients if they are captured and followed up with. That is why the sign-in and the same-day follow-up matter more than the refreshments.