I thought that “parish” referred to a bounded area or location in which all the Catholics are supposed to be registered at and attending a given Catholic church. Our priest refers to his “parish” as an area not just including the Catholics in his church, but including ALL the people who live in the parish, Catholic, non-Catholic, non-Christian, etc. He feels that he is responsible for the spiritual conversion of everyone living in his “parish,” not just Catholics.
A parish could also refer to an ethnic group that has permission from the bishop to attend a Catholic church outside of their bounded parish. E.g., in our city, there are an Italian, a Polish, and a Latino parishes, and people who wish to register there are invited to get permission from the bishop.
If this “geographical location” definition is correct, that would mean that a “faith community” is more exclusive, referring only to the people who actually attend or are registered to attend a certain Catholic church.