We use in to talk about where something is in relation to a larger area around it:
A:
Where’s Jane?
B:
She’sinthe garden.
I’ve left my keys in the car.
We use into to talk about the movement of something, usually with a verb that expresses movement (e.g. go, come). It shows where something is or was going:
A:
Where’s Jane?
B:
She’s goneintothe house.
Helen came into the room.
Compare
She’s gone for a walk in the garden.
She is in the garden walking.
She walked into the garden.
She entered the garden.
With some verbs (e.g. put, fall, jump, dive) we can use either in or into with no difference in meaning:
