This is the 3069th most frequent Russian word.
иностранцев
"Foreigners" or "of foreigners" (genitive plural form).
The word 'иностранцев' (foreigners) is the object of the verb 'обучают' (are taught), indicating the group of individuals receiving education.
В языковой школе обучают иностранцев.
In the language school, foreigners are taught.
Here 'иностранцев' (foreigners) serves as the object of the verb 'рассказал' (informed), specifying the audience being addressed.
Гид рассказал иностранцев о местных достопримечательностях.
The guide informed foreigners about local sights.
In this sentence, 'иностранцев' (foreigners) is part of the predicate, indicating individuals present in the location.