The Mezuzah

A mezuzah (plural mezuzot) is not that lovely case which adorns the doorposts of many Jewish homes--it is the parchment inside.
On the parchment is written the words of the Shema prayer, found in Deuteronomey, which contains the basic tenants of the Jewish faith and is the source of the mezuzah commandment.
Each doorway in a Jewish home should have a mezuzah on its right hand side (as viewed from the main entrance to the room). Bathrooms are the only exception to this rule.