Inside The Car, Inside The Train, Inside The Bus
noun, の adjective
The car inside is simply that, inside the car. This can be used for other means of transport too, so it can also mean inside the train or inside the bus.
しゃない
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
車内に人々がたくさんいます。
There are many people in the car.
バスの車内にはドライバーがいなかった。
There was no driver inside the bus.
先月、タクシーの車内にスマホをわすれたんです。
Last month, I left my smartphone in a taxi.