All Catholic parishes are churches, but not all churches are parishes. A “church” can include shrines, chapels attached to a school, hospital, or religious house, as well as an “oratory” or mission, which may be an annex or outreach of a parish. In my opinion, it is the presence - constant or occasional - presence of the Blessed Sacrament that makes a building, or room, a “church”.
A “parish” is usually a geographic area, though sometimes an ethnic designation, specifically assigned by the bishop, with a “pastor”, the priest having responsibility. A parish has some responsibility to everyone in its boundaries, including inactive Catholics or non Catholics. Most Protestants have what’s called “congregations”. If most members now live in a suburb, they simply sell the old building, and buy or build a new one convenient to where most live now. It is far more traumatic when a Catholic parish closes.
I don’t like the trend of some Catholic parishes to avoid using that word - for instance, “St. John’s Community”. Call me suspicious, but I have seen a hint of congregationalism, where the local church regards itself as autonomous, redefining its relationship to a “pastor”, who now becomes the hired employee of the congregation, just a “presider”; and the community wants to be only loosely affiliated with the bishop, not “under” a bishop. The “community” doesn’t regard the pastor or bishop as shepherds, but as equals. For awhile, every “community” was writing its own “mission statement”, different from other Catholic parishes. I think it’s only a short step to each “community” announcing which Catholic doctrines are currently relevant to it; and which aren’t; perhaps by means of a vote.
So, even though other kinds of Catholic churches also have a role, I urge that Catholic “parishes” be clearly defined as such.