Я начал изучать русский в 2012 году и ещё я не понимаю простые вещи!
It's not easy things, but basic things. But they are far far from simplicity.
Really good video is given above. Don't miss second one in the list of related things.
It's the basics of tone/emphasizing. But subject is much more bigger.
Commentator in the video says that order of "В Москву я приехал" is for emotioning. It's emphasizing also. Emotional emphasizing. В Москву, а не куда то еще.
"Ушел папа" also emphasizes "ушел" in emotional way. Something is wrong with his absence. Probably it was expected from him to stay there. But despite of it he gone! And this word is emphasized by tone and reordering.
But also it can be positive tone, not only negative. Context is important and this is really subject for books.