This is the 18229th most frequent Russian word.
чешские
"Чешские" means "Czech" (adjective, plural form) in English.
In this sentence, 'чешские' is used as an adjective, modifying the noun 'горы' (mountains) to indicate that the mountains are located in the Czech Republic or are associated with it.
Мы посетили чешские горы летом.
We visited the Czech mountains in the summer.
Here, 'чешские' functions as an adjective, describing 'традиции' (traditions) to specify that the traditions originate from or pertain to the Czech Republic.
Чешские традиции в этом городе особенно почитаемы.
Czech traditions in this city are especially revered.
In this sentence, 'чешские' modifies 'деликатесы' (delicacies), clarifying their origin as related to the Czech Republic.