Unlike a dragon ancestor who gets their power naturally or a wild mage who gets their power through a random event sorcerers that are arcane borns are actually made from magic. Whether they were created by some kind of magician or are simply magic incarnate arcane born sorcerers are capable of harnessing the magic that created them giving them a variety of abilities.

Arcane form

Starting at 1st level you are capable of using a bonus action to harness the magic that you are composed of in order turn yourself into an apparition of yourself made up of powerful magic for one minute. While in this form physical slide through you with ease giving you resistance to slashing, piercing, and bludgeoning damage. While in this form you can also cast first level spells without expending a spell slot. You can only enter arcane form once per long rest. 

magic body

Due to you being made of magic you also have resistance to it, giving you advantage to all spell saving throws.  

Arcane form extension

Starting at 6th level you can enter your arcane form by expending five sorcery points and when in arcane you can also use an action to regain an expended sorcery points. 

Elements of the arcane

Starting at 14th level when you enter arcane form you may also choose one damage type including fire, cold, lightning, force, or thunder damage and become resistant to it for the duration of your arcane form. Also at fourteenth level you can use an action to summon an elemental with a challenge rating of half your sorcerer level once per day.  
 
 

Pure arcane form

Starting at 18th level you learn to harness even more of the magic that created you allowing you to enter an arcane form made up of pure magical energy. When in this form you can now cast spells up to third level without a spell slot. At eighteenth level you also gain more control over your arcane form and can enter it once per short rest.