Muslims believe in something called "Ummah" which means "one community" .
That means that they see other Muslims as part of their family.
However, just like there are Protestants and Catholics within Christianity, there are different groups of Muslims such as the Sunnis and Shi'ites.
The differences within Islam first began in the 7th Century when the Prophet Muhammad died. There were disagreements as to who should lead the Muslim community.
Some Muslims wanted Muhammad's son in law, Ali, to succeed Muhammad. This group are what we now know as Shia.
Those who wanted a friend of Muhammad's (called Abu Bakr) to succeed Muhammad are known as Sunni.
Sunnis and Shi'tes have different versions of the Hadith (the book of Mohammad's sayings.) In turn, this means they have a slightly different understanding of Islam.
Overall, Islam is a diverse religion and there are different interpretations of the Qur'an.