Possessive Adjective and Possesive pronouns.

First we should know what is Adjective and what is pronoun:

Adjective : It describes a noun.

Pronoun: It takes the place of a noun.

Look at the following sentence pairs. One has an adjective (Which will tell who owns it, describes what it is, description about it), while the other has a pronoun (In adjective as it already explain, so in pronoun it will give required information). Examples:

1) My book is large. (My is an adjective because it modifies and describes about Noun book)   (Noun : Book, Possessive : My)

2) Yours is small. (Yours is an pronoun because in this sentence without telling about book it is giving direct answer yours is small, it means your book it small.

Your car is green. (Your is adjective same like above sentence, it shows what is green.)
Mine is red. (Mine is pronoun, takes the place of noun and gives indirect answer)

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Here is the possessive adjective: 
1) mi/mis  : My
mi libro
mis plumas

2) tu/tus : Your
tu libro
tus plumas

3) su/sus : his, her, your (formal), their
su libro
sus plumas

4) nuestro/nuestra/nuestros/nuestras : our
nuestro libro
nuestras plumas

5) vuestro/vuestra/vuestros/vuestras : your
vuestro libro
vuestras plumas

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The possessive pronouns are similar to the possessive adjectives, but they are normally used with the definite article and are more formal.

1) mine
el mío / la mía
los míos / las mías

2) yours (familiar)
el tuyo / la tuya
los tuyos / las tuyas

3) yours (formal), his, hers
el suyo / la suya
los suyos / las suyas

4) ours
el nuestro / la nuestra
los nuestros / las nuestras

5) yours (familiar)
el vuestro / la vuestra
los vuestros / las vuestras

6) yours (formal), theirs
el suyo / la suya
los suyos / las suyas

Note : Possessive adjective are used for short sentences and are casual, whereas possessive pronouns are used in long sentences and are like more formal sentences.

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Suppose you're talking to a friend and using casual form of Tu speech. Then here are few examples:

1) Mi libro es grande.
My book is large.

2) El tuyo es pequeño.
Yours is small.

3)Tu carro es verde.
Your car is green.

4) El mío es rojo.
Mine is red.

Notice how the same sentences change if we assume that you are talking to someone in a position of authority, using the more formal “usted” form of speech..

1) Mi libro es grande. (no change)
My book is large.

2) El suyo es pequeño. (formal)
Yours (formal) is small.

3) Su carro es verde. (formal)
Your (formal) car is green.

4) El mío es rojo. (no change)
Mine is red.

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Also, the definite article is usually omitted when the possessive pronoun comes after the verb ser:

1)El carro grande es mío.
The big car is mine.

2)El carro pequeño es suyo.
The small car is hers.

Notice the following below sentences, we cannot identify the gender. Weather it can be his or hers.

El carro grande es suyo.
The big car is his /hers.

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Well, in such cases El suyo, la suya, los suyos, las suyas can be clarified as follows:

1)El carro grande es suyo.
The big car is his. (unclarified)

2)El carro grande es de él.
The big car is his. (clarified)

3)La casa pequeña es suya.
The small house is hers. (unclarified)

4)La casa pequeña es de ella.
The small house is hers. (clarified)

5)Los carros grandes son suyos.
The big cars are theirs. (unclarified)

6)Los carros grandes son de ellas.
The big cars are theirs. (clarified)

7)Las casas pequeñas son suyas.
The small houses are theirs. (unclarified)

8)Las casas pequeñas son de ellos.

The small houses are theirs. (clarified)