When you “swear” something, you are making a promise that what you are saying is true. This promise is often made over an object that is holy to you (such as the Bible, the Torah, or the Koran), or in the name of a deity you believe in (such as God or Allah). This is also called taking “an oath.” For people who do not want to swear over a holy book or in the name of a deity, this promise is called “affirming.”
It is a criminal offence to swear false information on purpose. It is considered “perjury,” or lying under oath. The punishment can range anywhere from a fine up to 14 years in prison.