Tefillin are passages from the Torah that are written on parchment and are placed within leatherbatim (casements), with leather straps attached to the batim. These straps are used to bind the batim and the parchment Torah passages within them on one`s arm and hand and on one`s head.
The four passages are written on a single parchment in the hand Tefillin (tefillin shel yad), while in the head Tefillin (tefillin shel rosh) each passage is written on a separate parchment, so that each passage can be placed within one of the four compartments in the head Tefillin. These inner compartments of the head Tefillin also are called "batim."
The four passages are: "Consecrate to Me every first-born" (Exodus 13:1-10) "And when the L-rd has brought you" (Exodus 13:11-16) "Shema Yisrael - Hear, O Israel" (Deuteronomy 6:4-9) "If, then, you obey" (Deuteronomy 11:13-21)
There are two traditional methods for the writing of the Torah passages of the Tefillin, that of Rashi, and that ofRabbenu Tam, Rashi`s grandson. According to Rashi, the passages are written and are placed within the batim in the order in which they appear in the Torah, namely: "Consecrate to Me," "And when the L-rd has brought you," "Hear, O Israel," and "If, then, you obey." Rabbenu Tam places the passage of "If, then, you obey" before "Hear, O Israel."
Everyone puts on the Tefillin of Rashi. Some people, in order to fulfill the obligation of Tefillin according to both views, also put on the Tefillin of Rabbenu Tam at the end of the Shacharit service, without reciting an additional blessing.