I wonder about the different versions of you... aap,, tum and tu... they seem to be used interchangeably and that is not maybe true...
Please refer to the last section of this page to understand this concept! :D
मैं आगे हूँ और आप पीछे हैं।
मैं आगे हूँ और तुम पीछे हो।
मैं आगे हूँ और तू पीछे है।
Aap is a formal version of you. It is used for people of respect.
Tum is neutral but it is 75% informal and 25% informal.
Tu is a informal word.
Although it is used but Tu is not a hindi word.