When a place is locked and someone finds a way to get in, they're "breaking into" that place.

Burglars "break into" houses, cars, and so on. On movies, they may even "break into" places like bank vaults.

But you can also use the phrase "break into ___" to talk about getting into your own house, car, office, etc. if you're locked out:

I locked myself out of the house. I tried to break in with a credit card like they do on T.V., but no luck.

Notice that when you use the phrase by itself, it's "break in". When you name the place that someone breaks into, it's "break into ___".