“it's a branch of philosophy” It is certainly not. Philosophy questions, theology provides answers you can’t question as God exists and these are the laws you obey or you die on Earth and then burn in hell for Eternity, and God loves you.

Philosophy can be “does the concept of table pre-exist the table, or the fact to create a table creates the concept of table then will expend the concept table to all kinds of tables”. That is fascinating… Basically, do you cut a tree then put you meat on it and find out it is very handy, and you can make it portable, or do you think first, if I cut a tree and make it portable, I can put my meat on it during my hunting party and it will be easier to handle it for the seasoning?

In theology, you can’t think before. You accept a set of rules, and then you discuss what God intended to say as it is quite opposite from one chapter to the other. As TR tried to convinced people that to rape, kill and enslave others is ok because the others were not of the good religions, so their human rights just vanish, an opinion shared by the ones like ISIS. If God says so, it is OK.
If you question the set of beliefs, it is a heresy when it failed, as the Cathars and the Bogomils learned it hard way. If successful it becomes a new Religion as seen in various branch of Christianity.