Here in Texas (Houston, to be exact) they recently opened a new co-cathedral. What is the difference between a cathedral and co-cathedral? And what is the difference between a bishop and an archbishop? I didn’t know and one of my protestant friends asked me and I said, “I don’t know, but I know where to find out”
A cathedral is the church of the bishop’s seat (cathedra). Co-cathedrals are two cathedrals in a diocese that share the honor of being the bishop’s seat. Sacred Heart in Houston and St. Mary’s in Galveston are both cathedral churches of the bishop.
Here’s an article on Cathedrals:
Here’s an article on Bishop versus Archbishop: