Our crucifix, icons and other articles are examples of what we call sacramentals. According to the Catechism of the Catholic Church, sacramentals are sacred signs instituted by the Church to prepare us to receive the fruit of the sacraments and to sanctify different circumstances of our lives (no. 1677).
Practically speaking, the myriad of little things that are sacramentals are the parts of catholicity that jostle against us in our everyday life, those little extras that often tell others we are Catholic. They are the images, actions and blessings that are unique to our faith; those sometimes humble reminders of what the Catholic faith is all about, like the crucifix on our wall.