In your question, you ask about “sectrenism.” I believe that you are really referring to “sectarianism” and I will give my answer based on that assumption. Sectarianism can be defined as the belief that people of other sects are in some way inferior to people who are of your sect. Sectarianism tends to be manifested in actions that discriminate against or abuse people of other sects.
In order to understand sectarianism, we must first understand what a sect is. A sect, in this context, is one offshoot of a given religious faith. People of different sects belong to the same general religion, but are not in the same subgroup. So, we can say that Roman Catholics and Protestants are members of different sects and we can say that Sunni and Shi’a Muslims are of different sects. However, we cannot say that Jews and Muslims, for example, are from different sects as they are not generally seen as part of the same faith.
Sectarianism involves discrimination against or abuse of people from other sects. We see examples of sectarianism around the world. Perhaps the most famous sectarian conflict today is the conflict between Sunnis and Shi’a in the Muslim world. These two sects (at least in the Middle East) are sectarian enough that they engage in violence against one another fairly frequently. The civil conflict in Northern Ireland is also at least partly a sectarian struggle as Protestants and Catholics hate one another due in part to their religious differences.
In sum, then, sectarianism is discrimination against or abuse of people from other offshoots of your own faith. The word is not generally used to refer to conflict between people of different faiths.
Sectarianism is basically discrimination based on different beliefs. A denomination, or sect, is a group within a faith or religion that usually share the same ideas. There can be several groups within a faith who have the same ideas but different practices, which can lead to narrow-mindedness and thinking certain groups are superior.