What does this sentence/idiom/phrase mean?

I saw a sentence in a book:

When George heard that the meal was on the house, he went to thank the restaurant owner for the free food.

The sentence does not make sense to me. I tried Google translating to other languages, but did not work as well.

Is there a specific idiom or phrase that I'm not familiar with?

Can anyone help me with this?

Solution 1:

"On the house" means that you are given something for free, that you would usually pay for.

(of a drink or meal in a bar or restaurant) at the management's expense; free.

Lexico

You can think of the sentence like this:

When George heard that the meal was on the house given to him for free by the owner, he went to thank the restaurant owner for the free food.