The word than is used in comparative constructions. Its complement, in your sentence mine, is one of the comparands.

Our car is older than their car.

Our car is older than theirs.

With different you will encounter from and than, and also to now and then.

Our car is different from|than theirs. Ours is AWD with a CVT and theirs is a standard transmission, but otherwise they look identical.

The word than is used in comparative constructions. Its complement, in your sentence mine, is one of the comparands.

Our car is older than their car.

Our car is older than theirs.

With different you will encounter from and than, and also to now and then.

Our car is different from|than|to theirs. Ours is AWD with a CVT and theirs is a standard transmission with front-wheel drive, but otherwise they look identical.