OK here i'll break it down to you. in Islam the prophet said that the Christians will divide into 71 sects ( as you may see the differentiation in Christianity ) the Jews into 72 sects and Islam into 73 sects. he continued to add that all of those sects will be in the hell fire except one...and those are who followed him and his companions. OK so shia is one of the sects that will go hell fire and there is many many proofs for this and the sunni's are those who follow the prophet and his companions, however many claim to be sunni and are not. shia is one of 72 deviated sects in Islam. anymore questions? inbox me, i'll be happy to help!
like- catholic and protestant in christianity- only pertaining to islam and just one more reason for them to fight each other.
It's part of Islam religion. They're two different religions within Islam, but they're very similar.