"Tú" is a personal pronoun; "Tu" is a possesive adjective
"Él" is a personal pronoun; "El" is an article
"Té" is a noun; "Te" is a personal pronoun
"Mí" is a personal pronoun; "Mi" is a possesive adjective
"Dé" is a form of the verb "dar"; "De" is a preposition