N.B: These words change their form depending on whether the word they are going with is masculine, feminine, singular or plural. NOT the person who owns the object.
eg: mon livre (singular and masculine)
ma trousse (singular and feminine)
mes crayons (plural and masculine)
mes règmes (plural and feminine).
ton, ta, tes = "your" when talking to one person you know well (Tu)
votre = "your" when talking to someone you don't know well or two or more people.