This is the 11049th most frequent Spanish word.
du
"Du" is not a word in standard Spanish.
The word 'tú' is used here as a subject pronoun meaning 'you' in an informal context.
Tú tienes el poder de cambiar el mundo.
You have the power to change the world.
'Tú' serves to emphasize the subject 'you' in this personal greeting.
¿Cómo estás tú hoy?
How are you today?
The subject pronoun 'tú' is used in a statement to establish who is performing the teaching action.