Heresy is a belief or opinion that does not agree with the official belief or opinion of a particular religion.  Often a religion contains ideas that are heretical to many other religions.
Heresy as a Crime
Heresy has often been considered and treated as a crime in certain religious cultures such as Christianity, Judaism and Islam. While many countries no longer consider heresy to be a crime there are still countries in which heresy is punishable by death. It should be noted, however, that like blasphemy, heresy is a victim-less crime. The criminalisation of heresy is contrary to freedom of speech and a violation of the separation of church and state.
In 2014, Mohsen Amir-Aslani was executed for heresy, in which he taught his own non-literal interpretation of the Qur'an and making "innovations" to Islam. He was also accused of insulting Jonah and sexual relationships within his Qur'an reading group. The Gonabadi dervishes also face persecution within Iran for deviating from the "approved" interpretation of Islam.