In English, we use one to avoid repeating the same word twice; for example, The blue dress is more beautiful than the red one.
In Spanish, you can say el or la before an adjective to avoid repeating a noun.
Another way we avoid repeating nouns in English is to use words like mine and yours. For example, in Your car is faster than mine, mine is used to avoid saying my car.
In Spanish, mine is el mío or la mía, and yours is el tuyo or la tuya.
Ese perro es más gordo que el mío.
That dog is fatter than mine.
Mi camisa es roja y la tuya es verde.
My shirt is red and yours is green.
Queremos una falda bonita como la tuya.
We want a nice skirt like yours.