This is the 1082nd most frequent Polish word.
kościele
"Kościele" means "church" in the locative case in Polish.
The word 'kościele' here is used in the locative case indicating the location.
Byłem w kościele wczoraj.
I was in the church yesterday.
In this sentence, 'kościele' is applied in a similar locative usage context referring to the place where the action of praying happens.
Modliliśmy się w kościele za zdrowie naszej rodziny.
We prayed in the church for the health of our family.
The term 'kościele' is applied as a descriptor within a prepositional phrase specifying the routine activity's location.