What is the meaning of Remember: A noun does not immediately follow a possessive pronoun while a possessive adjective always comes before a noun ?

A possessive adjective always comes before the noun because it qualifies the noun. But a possessive pronoun is not placed immediately after the noun. For example:

This is my house. (Possessive adjective)

That house is mine. (Possessive pronoun)

'House' acts as a noun in both the sentences.