In Spanish, some pronouns change when they are placed after a preposition:
Yo changes to mí.
Tú changes to ti.
All the other persons remain the same. This is the equivalent of for me, for him, for them, etc. in English.
Tengo una carta para ti. (I have a letter for you.)
¿La bufanda es para mí? (Is the scarf for me?)
Juan tiene un libro para nosotros. (Juan has a book for us.)
¿Tienes un minuto para ella? (Do you have a minute for her?)