Inside, In, Into & Within
Inside & In are the same in many cases.
We are in the building -> We are inside the building
The clothes are in the car -> The clothes are inside the car
Inside means that the thing is physically enclosed - in a building with walls, in a vehicle etc.
Use in where you are not physically surrounded:
I live in Poland.
My birthday is in March.
I play guitar in a band.
Into implies movement or transformation:
I jumped into the swimming pool.
We went into the house.
The car crashed into a shop.
You can use into & in when you use verbs drop, throw, fall, put.
He put the money into/in his pocket.
I threw the paper cup into/in the trash.
He lost his balance and fell into/in the sea.
means inside or not further than a particular area or space:
Most car accidents occur within 10 kilometers of home.
you can use to refer to time:
I've noticed her change within a very short time.
You can also use within to describe a person's inner feelings (in this case, you can also use "inside"):
John tried to hide the anger burning within/inside him.
Within does not mean the same as in. Within stresses that something is not further than a particular area or space or not later than a particular time:
John always have tea in the afternoon (Not: I always have tea within the afternoon).