This is the 619th most frequent Russian word.
внутри
"Inside."
Here, 'внутри' is used as a preposition meaning 'inside', specifically a location within an object (the car).
Я нашёл ключи внутри машины.
I found the keys inside the car.
In this sentence, 'внутри' indicates the location within a defined space (the room) and is used adverbially.
Внутри комнаты было тихо и темно.
Inside the room, it was quiet and dark.
Here, 'внутри' denotes an inner state or introspective location, often used metaphorically to describe internal feelings or self-awareness.