I noticed while in church some people make the sign of the cross after a priest is finished with his homily. Is this mandatory? were does this come from and what does it mean?
Prior to the liturgical reforms of the Second Vatican Council the sign of the cross was made before and after the homily. The reason that this was done was that the homily was not thought of as integral to the Mass. Thus when a homily was given the sign of the cross before and after the homily was used a sign that they have sort of “stepped outside” the Mass for the homily and then reentered it.
Today the Church sees preaching as part of the Mass and thus no longer directs for the sign of the cross to be made for the homily. What you’re witnessing is most likely people who grew up with the older rite and its rituals and they still perform them out of either habit or personal piety. There’s nothing wrong with it as long as its not considered mandatory for everyone.