A Mezuzah is a parchment scroll that has been written by a professionally trained scribe. Every Mezuzah contains the exact same inscription, including two portions of the Torah that discuss the Jewish Faith, as well as the Shema Yisrael: "Hear O Israel, the Lord Our God, the Lord is One."
The Mezuzah is traditionally attached to the doorposts of a Jewish dwelling. It is a symbol of G‑d's watchful care over the house and its dwellers. The name of G‑d, Sha-dai, which appears on the reverse side of the parchment, is an acronym for the Hebrew words which mean 'Guardian of the doorways of Israel.' The placing of a mezuzah on the doors of a home or office protects the inhabitants -- whether they are at home or away.