What's "run out of" mean? Is this an idiom?

Native speaker’s answer
Rebecca
When talking about a quantity or supply of something, to "run out [of]" means to be exhausted or used up. In this video, "I've run out of ways to say 'congrats'" means "I don't have any more ways to say 'congrats'." Ex: I ran out of toilet paper at home. Ex: Can you pick up some milk? We ran out.