Fundamentally, it's about the succession dispute after the Prophet (pbuh) passed away. Sunnis consider Umar, Usman and Abu Bakar to be the rightful successors. Shia's don't recognize any of them and go with the Prophet's son-in-law, Ali, instead. Sunnis also recognize Ali, but only as a subsequent successor after the other three.
You will never see a Shia named Umar, Usman or Abu Bakar. Also, Ali (and his martyred son Hussain) are central in Shia culture, although they are revered by Sunnis also.
Most ordinary Shias and Sunnis are not militant about the differences. It's used more by Iran and the oil-rich Arabs as a political weapon.
you could have avoided that question, because it can to derail us to the sectarian flame war. Regarding naming, I can say the same thing about some shia names that some Sunnis might not have but lets leave it there but to be fair you are more or less correct, although I know shias with Usman Ali name.
I more or less will agree with your post. I myself have family members from both sect so I have no prejudices and respect them both and am proud and really lucky to see both sides.
To pretty much end this debate here and prevent any possible flaming I would sum up the differences as under.
For a Pakistani. A Sunni is one who came up with the concept of 2 nation theory, another Sunni dreamt of a separate country and then convinced a Shia to lead the struggle and get us Pakistan. That Shia never ever let the sect come between him and rest of the Pakistanis and even willed that his prayers be offered by a Sunni Alim.
Yes I am talking about our founders Shah Waliullah, Alama Iqbal and Quaid e Azam Muhammad Ali Jinnah.
Pakistan Army is the best example of this bond where these brothers fight and defend the country side by side.
Shia & sunni share the beliefs that are required for becoming a Muslim like Oneness of Allah & belief in Muhammad PBUH prophet hood, Holy Quran and Judgement day etc
Shia & Sunni do have differences though and those differences are with these socalled Muslims who have hijacked the religion, in the history they have been called Khawarij or Takfiris ( current versions, Taliban,TTP, Al Qaeda, LeJ) for whom every Shia & Sunni is a non- Muslim and deserves painful death if he doesn’t conform to their Islamic interpretation.