On the house This phrase means “免费提供的”. For example, when you finish your dinner at a nice restaurant, the server put a plate of fruits on your table and says to you: Please enjoy the dissert. It's on the house. So you don't need to pay for things that's on the house. There is another word "complimentary". It's the same meaning. Some dance club give people complimentary tickets to attract them to come. The tickets are free but the drinks and foods are very expensive. Sample sentence: I always go to hotels that have complimentary breakfast. That really saves a lot of money.