The possessive pair
Every person has two possessive words in English. One goes before the noun. One stands alone.
I → my book, the book is mine
You → your bag, the bag is yours
He → his coffee, the coffee is his
She → her phone, the phone is hers
We → our house, the house is ours
They → their car, the car is theirs
It → its tail (no second form for 'it')