Laïcité, or secularism, has its roots in the 18th century enlightenment. It was originally signed into law in 1905 by France's Third Republic in Article 1 of the French Constitution which guarantees freedom of conscience. This idea was further defined by the Fifth (the current) Republic which states that this "assures the equality of all citizens before the law, without distinction to their origin, race or religion. It respects all religious beliefs." However, in Article 2 it states that "the Republic does not recognize, compensate or subsidize any religion." This second article often overshadows Article 1, which states that there is State neutrality with regard to religion.
On a personal level, faith is seen as a private matter. The State is a "no God" zone, and State employees are expected to remain neutral, with no religious symbolism displayed while on the job. For many people, faith is seen as something that needs to be kept to yourself. Blatant outreaches and proselytizing are seen in a negative light, and can even be against the law in many cases. In fact, our French friends told us about an experience they had recently where having a Christian baptism ceremony at a lake was seen so negatively that the police were called at least twice during the event. While it wasn't illegal, outward, expressive Christian practices can have an extremely negative effect on the community instead of a positive one.