This is the 258th most frequent Russian word.
некоторые
"Some" or "certain."
In this sentence, 'некоторые' is used as a determiner to denote an unspecified but counted subset of people among a group.
Некоторые люди предпочитают путешествовать зимой.
Some people prefer to travel in winter.
Here, 'некоторые' refers to particular coins that are specified as rare, implying a selection from the collection.
В моей коллекции есть некоторые редкие монеты.
In my collection, there are some rare coins.
In this example, 'некоторые' indicates a subset of people who hold a specific belief regarding health benefits of sports.