Inside has developed from being a preposition simply meaning withing a building, to meaning just about anywhere in the world. It is an incredibly unhelpful way to assist anyone who is in genuine need of assistance in locating something. It can also be a reference to someone's testes.

A girls inside of vagina.

something you say, after you've joked with your friends in front of a group of other people and they look baffled...
insiderjoke

In prison.

To be in something or somewhere.

I did an inside job

inside joke between friends