As perla said, they´re all pronouns, more specifically referring to the 2.person singular. However, they belong to different types of pronouns, namely subject pronouns, object pronouns and prepositional pronouns. Tú - You (subject pronoun) When the pronoun is the subject of a verb: You walk - Tú caminas; You speak english - Tú hablas inglés. Te - You (object pronoun) When the pronoun is the object of a verb: "I don´t see YOU" - "No TE veo". This holds true for indirect objects as well as direct objects. Ti - You (prepositional pronoun) Prepositional pronouns is used after a preposition: This flower is for YOU - Esa flor es para TI There are some exceptions to the rule of prepositional pronouns: - "con": conmigo/contigo instead of "conmi"/conti" - entre (between), excepto (except), incluso ("including" or "even"), menos ("except"), salvo ("except") and según ("according to") -- These all use the subject pronouns: "Yo" and "Tú" instead of "Mi" and "Ti". Source: spanish.about.com

Sorry I just did a typo by accident! However what I was trying to say is that they are all pronouns use in different ways. You just have to see the one that falls in your sentence.

They are all pronauds

Thank you so much for your input!!! it helped a TON!! :)

"Tú"," ti" y "te" son pronombres personales para la segunda persona del singular. Pronombres personales, son los que señalan a las personas gramaticales. Generalmente van delante de un verbo y no suelen acompañar a los nombres. Ej: No "te" veo. Este vestido es para "ti". "Tú" sabes leer.