My is a possessive adjective and goes before a noun to show who or what owns it.
- This is my book.
- Everyone was surprised by my cooking skills.
Mine is a possessive pronoun and is used to replace a noun so you don’t repeat it.
- ‘Whose book is it?’ ‘It is my book.’
‘Whose book is it?’ ‘It is mine.’
(mine replaces the noun book) - The phone on the table is my phone.
The phone on the table is mine.
(mine replaces the noun phone)
