Complex sentence: The Ruthenian Catholic Church is rooted among the Rusyn people who lived in Carpathian Ruthenia, in and around the Carpathian Mountains; the area is where the borders of present-day Hungary, Slovakia and Ukraine meet.
Split into simpler sentences: The Ruthenian Catholic Church is rooted among the Rusyn people who lived in the region called Carpathian Ruthenia, in and around the Carpathian Mountains. This is the area where the borders of present-day Hungary, Slovakia and Ukraine meet.