There are many different sects that caused division in Islam, and this goes clearly against Islamic teachings. Allah Says in The Noble Quran (interpretation of meaning), “And hold firmly to the rope of Allah and do not be divided. Remember Allah’s favor upon you when you were enemies, then He united your hearts, so you—by His grace—became brothers” (Quran 3:103). However, this raises the question: how does one know which sect in Islam is the right one? The Prophet Muhammad (Peace and Blessings be upon him) clearly answered this in a hadith where he said, “’The Jews split into seventy-one sects, one of which will be in Paradise and seventy in Hell. The Christians split into seventy-two sects, seventy-one of which will be in Hell and one in Paradise. I swear by the One Whose Hand is the soul of Muhammad, my nation will split into seventy-three sects, one of which will be in Paradise and seventy-two in Hell.’ It was said: ‘O Messenger of Allah, who are they?’ He said: ‘The main body'” (Sunan Ibn Majah 3992). In another narration, He (Peace and Blessings be upon him) said, “Those who will remain on the path which I and my companions are on today.” Therefore, it is clear that he is talking about the Sunnis, or those who follow The Sunnah of The Prophet Muhammad (Peace and Blessings be upon him). The Sunnis make up about 90% of the Muslim population, which is clearly the vast majority of Muslims. However, the name Sunni was given to clarify and distinguish between all the other sects, but one should just call himself a Muslim unless needed to clarify, because that is what the Prophet Muhammad (Peace and Blessings be upon him) and his Companions were called. What’s amazing is that despite the different sects in Islam, they use The exact same Quran! None of them have added Chapters, Verses, Pages, etc. These sects only interpret things they want to in a different way for their own benefit, but The Text itself is still the same. This is because the way The Noble Quran has been Preserved is a rigorous method, namely through Memorization. Unlike with other religions such as christianity, different sects actually have different books.
And Allah Knows best.