A schism is basically a break up. A divorce. A separation.
Members of religions are prone to have schisms, usually over a minor point of doctrine. The CRC and RCA broke apart because the Dutch immigrants who became the CRC didn't think Christians should be members of lodges.
One might argue, I suppose, that the history of Christianity is one of separation. First, Christians separated from Jews. Then Orthodox (eastern) Christianity separated from the Roman Catholic Church. After that came the Reformation which created Lutheranism, Calvinism, the Anabaptists, Arminians and a big bunch of others that I can't remember. After that comes Methodists, Baptists and Pentecostals.
At least.
I'm sure that there are entire branches of Christianity that I am skipping in this little digression. I'd pick on other religions too (I doubt they're much different), but Christianity is what I know best, eh?
One of my theology profs once argued that schism is not necessarily bad. It allows people with irreconcilable differences to concentrate on something other than the difference. Once a denomination splits, they can work on fulfilling their responsibilities as Christians (ranging from social justice to evangelism) rather than pointless fighting.
Someday, once the anger has past, they may even come together in different (yet Christian) groups in a spirit of ecumenism.