"Thank You For Your Service" - What does that phrase really mean?

I have not seen the movie yet, but my wife who is not only a spouse of a service member but also a daughter of one. She was astounded at the movie and said it was nothing like she expected. She loved it. And can't wait for me to see it when it comes out. Also the phrase means that there are people out there who respect the things that I have done for them and the sacrifices that I took for them. The appreciated them and they were not just words to them either. I could tell that they really meant what they said.