Sunni and Shia are two major sects in Islam

It started out when the question of who would take over once the Prophet Muhammad SAW died. OBviously, the answer would be Abu Bakr.

A Sunni Salafi is one who follows the Prophet Muhammad SAW’s way

I guess Shias believe that Ali ibn Abu Talib, the fourth khalifa and the Prophet Muhammad SAW’s cousin, should have taken over.

The disagreement to choose Abu Bakr or Ali is what truly sets Shias apart from Sunnis. Another difference lies with the Mahdi. Shias believe that the Mahdi is already on earth but Sunnis believe that he’s yet to come.

You can trace the persecution of Shias to the Umayyad, then the Abbasids,  the Ottoman empire, and under Saddam Hussein

So yea, hopefully I answered your question

In my opinion, I wish for no division. After all, we all are Muslims regardless of who we believe to have been Prophet Muhammad SAW’s successor. The Quran calls for no division. It just adds to how perfected Islam is as a religion but the ummah is not completely perfect.