You have a bond with an elemental spirit that helps you in battle and you help it. You both have formed a bond with one another allowing abilities to enhance each other.

Elemental Call

At level 1 you gain the ability to summon an elemental ally ( as though the Summon Elemental spell). As an action you can summon your ally to an unoccupied area within 30ft of you. This style of the summon can be done once per day, and the summon lasts for 1 minute. When you later gain sorcery points you can spend sorcery points to extend its duration by 1 hour per point spent when you summon the creature.  After level 3 in this class you can expend a spell slot to summon this creature again. Either of these two listed ways to summon do not require concentration to maintain the summon. When time is up or the creature reaches 0 hp it disappears until summoned again. The summoned elemental has these changes to its stat block:

-AC is equal to 13

-HP is equal to 20+10 per spell level spent to summon this creature (if no slot used then it is just 20)

-It has hit die of 1d10 per spell level spent (min 1d10 if no slot used).

-It only has a normal 40ft speed regardless of form, So no fly,swim,nor burrow speed

-It has no resistances nor immunities

-it loses multiattack.

-its size is small

Elemental Bond

at level 6 your bond grows stronger. Your elemental's attacks now count as magical for the overcoming damage resistance and immunity. It also obtains these changes to its statblock:

-Its AC is equal to 14 + the level of the spell slot spent to summon it

-its HP is equal to 40+10 per spell slot spent to summon the creature (if no slot used then it is just 40hp)

-hit dice is now equal to 5+spell slot spent

-It has full use of any of its listed speeds of the given form summoned (fly for air, swim for water, etc)

-It has all its listed resistances and immunities of the given form summoned.

-it gains multiattack, and it can make 2 slam attacks. (it does not use its normal multiattack listed on its stat block)

-Its size is medium or large

-any spell cast with a range of self can also be cast on your elemental summon from its place, and any triggering attack against your summon that would trigger a reaction against yourself that reaction may be used (ex. if you have the shield spell and your summon is attacked you can cast shield to protect your summon instead of yourself). you gain the ability to expend a spell slot and heal your summon by 1d8+CHA mod x spell slot spent as a bonus action. You also gain a resistance of your choice that matches one of your summons resistances. You may spend a sorcery point to allow your summon to take the dash or disengage action as a bonus action.

You also can spend 2 sorcery points to increase the summon's damage die by 1 when you reach 10th level in this class. This increase lasts for 10mins.

Bonded Attunement

At level 14 you now gain one of your summon's speeds (fly, swim, or burrow) and you can now make 3 attacks with your summon's multiattack. You also can spend a sorcery point to increase your summon's reach by 10ft till the end of your next turn.

Bond Perfected

At 18th level your bond has become perfected. You can now spend 3 sorcery points to increase the summon's damage die by 2. You no longer need to decide the elemental's form as it obtains all its listed immunities and resistances as well as every listed move speed. Your elemental is all its forms in one. In addition you can spend 5 sorcery points to merge with your summon. When you merge your summon gains half your hit points  to its health as temp hp(this does take half your hit points away while merged), you are considered to have full cover, it can now make 4 attacks with its multiattack ability. This merge lasts for 10 minutes. In addition  when the merge ends if the summon has any of the temp hp it obtained from the merge left over then you restore you health by that amount. (ex. if your health was 100 then upon merge you would go down to 50 and the summon would have 50 temp hp, then if the merge ended without the form dying and it had 30 temp hp left from your health pool then you gain those back going to 80hp). The only spells able to be cast while merged must have a range of self