"Præsten fortæller befolkningen om religionen."
Translation:The priest is telling the population about the religion.
Although 'the religion' is an accurate translation, in English you would just say 'religion.' Words that are in the definite form in Danish are often indefinite in English.
Well, there is quite a difference between speaking about a specific religion or religion in general. I the sentence said "about religion", the Danish sentence had to be different also.