Possessive Pronouns are called so because they show the ownership.
They are declined according to gender, number and case of the possessed object.
Это моя машина. = This is my car.
То твой телефон. = That is your phone.
Это ваше вино. = This is your wine.
Это мои ключи. = These are my keys.
Sometimes you don’t want to say “This is my book”, but just “This is mine”. In this case, you should use the neuter pronoun:
Это моё, а то твоё. = This is mine, and that is yours.
Bellow is the table of singular Possessive Pronouns in the Nominative case.
my | your (informal) | your (polite/ plural) | his/its | her | our | their | whose? | |
он | мой | твой | ваш | его | её | наш | их | чей? |
она | моя | твоя | ваша | его | её | наша | их | чья? |
оно | моё | твоё | ваше | его | её | наше | их | чьё? |
они | мои | твои | ваши | его | её | наши | их | чьи? |