What is the difference between mammals and other animals

Hi,

Mammals are animals that mostly give birth to young ones while, other animals such as birds and fishes lay eggs.

They feed milk to their babies through an organ called mammary gland but other animals do not have this organ.

They have hair or fur on their bodies not feathers which are present on body of birds.

They respire through lungs but other animlas such as fishes respire through gills.

They have external ears.