This is the 8530th most frequent Russian word.
ночные
"Ночные" means "night" or "nocturnal" (plural, related to night).
Here, 'ночные' is an adjective describing 'звёзды' (stars), indicating their connection to the night.
Ночные звёзды сияют на небе.
The nighttime stars shine in the sky.
In this sentence, 'ночные' is an adjective modifying 'прогулки' (walks), highlighting the time of day (night) when these walks occur.
Она обожает ночные прогулки по городу.
She loves nighttime walks around the city.
Here, 'ночные' qualifies 'клубы' (clubs), specifying the type of clubs that are associated with nighttime activities.