You literally get the dragon born's ability to breath an element and be resistant to the same element except you can add a status ailment resistance and add the same status ailment to your breath weapon. Keep in mind that enemies can resist the status ailment of your breath.

You can pick up an ability from your not dragon parent. You can also pick up the racial feats of your parent race.

Dwarf- +1 to constitution and either dwarven toughness, resilience, or stone cunning

Elves- +1 to dexterity and trance plus keen senses or fey ancestry 

Gnomes- +1 to intelligence and gnome cunning or tinkerer

Halflings- +1 to dexterity and lucky

Half-orcs- +1 to strength and either menacing or relentless endurance

Humans- +1 to whatever you want and a feat of your choice

Tieflings- +1 to charisma on top if what you already get and either hellish resistance or infernal legacy

Goliaths- +1 to strength and powerful build

Aarakocra- +1 to dexterity and either flight or talons

Aasimar- +1 to charisma and celestial resistance

Bug Bears- +1 to strength and long limbed or surprise attack

Firbolgs- +1 to wisdom and speech of beast and leaf

Goblins- +1 to dexterity and furry of the small

Hobgoblins- +1 to constitution and saving face

Kenku- +1 to dexterity and mimicry

Kobolds- +1 to dexterity and pack tactics

Lizard folks- +1 to constitution and natural armor

Orcs- +1 to strength and aggressive

Tabaxi- +1 to dexterity and feline agility, claws, or cats talent

Triton- +1 to strength or constitution and amphibious or control air and water

You have small wings on your back and while they aren't enough to fly they are enough to slow your decent allowing you to take no fall damage and move a distance equal to 3 time the fall height.

You get a 60ft of dark vision not much else to say