Tefillin is a daily mitzvah involving boxes with Torah verses strapped to one’s arm and forehead, that is incumbent on men past bar mitzvah, similar to how a mezuzah is a scroll for a doorway. They might seem unrelated, but they are both mentioned together in the Torah for God’s protection. A large effort is going on, with organizations encouraging Jews to make sure they are being used, as specifically mentioned in the Shema:
Place these words of Mine upon your heart and upon your soul, and bind them for a sign on your hand, and they shall be for a reminder between your eyes… And you shall inscribe them on the doorposts of your house and on your gates - so that your days and the days of your children may be prolonged on the land which the L-rd swore to your fathers to give to them for as long as the heavens are above the earth.
These are not protective objects to be thought of as an idol, but that if one uses everything—body soul and home—to direct its uses for holy purposes, God will reward that, with tefillin and mezuzahs as the embodiment of that. They serve as a reminder of the eternal bond between the Jewish people and their faith, offering strength and purpose during challenging times.