The verb subir means to go up, usually up the stairs.
Tú subes is 2nd person singular.
1st person singular would be - Yo subo, and plural - Nosotros subimos.
2nd person plural would be - Vosotros subís.
3rd person singular would be él/ella/Usted sube, and plural - ellos/ellas/Usteden suben.
